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EVP_ENCRYPTINIT(3ossl)              OpenSSL             EVP_ENCRYPTINIT(3ossl)



NAME

       EVP_CIPHER_fetch, EVP_CIPHER_up_ref, EVP_CIPHER_free,
       EVP_CIPHER_CTX_new, EVP_CIPHER_CTX_reset, EVP_CIPHER_CTX_free,
       EVP_CIPHER_CTX_dup, EVP_CIPHER_CTX_copy, EVP_EncryptInit_ex,
       EVP_EncryptInit_ex2, EVP_EncryptUpdate, EVP_EncryptFinal_ex,
       EVP_DecryptInit_ex, EVP_DecryptInit_ex2, EVP_DecryptUpdate,
       EVP_DecryptFinal_ex, EVP_CipherInit_ex, EVP_CipherInit_ex2,
       EVP_CipherUpdate, EVP_CipherFinal_ex, EVP_CIPHER_CTX_set_key_length,
       EVP_CIPHER_CTX_ctrl, EVP_EncryptInit, EVP_EncryptFinal,
       EVP_DecryptInit, EVP_DecryptFinal, EVP_CipherInit, EVP_CipherFinal,
       EVP_Cipher, EVP_get_cipherbyname, EVP_get_cipherbynid,
       EVP_get_cipherbyobj, EVP_CIPHER_is_a, EVP_CIPHER_get0_name,
       EVP_CIPHER_get0_description, EVP_CIPHER_names_do_all,
       EVP_CIPHER_get0_provider, EVP_CIPHER_get_nid, EVP_CIPHER_get_params,
       EVP_CIPHER_gettable_params, EVP_CIPHER_get_block_size,
       EVP_CIPHER_get_key_length, EVP_CIPHER_get_iv_length,
       EVP_CIPHER_get_flags, EVP_CIPHER_get_mode, EVP_CIPHER_get_type,
       EVP_CIPHER_CTX_cipher, EVP_CIPHER_CTX_get0_cipher,
       EVP_CIPHER_CTX_get1_cipher, EVP_CIPHER_CTX_get0_name,
       EVP_CIPHER_CTX_get_nid, EVP_CIPHER_CTX_get_params,
       EVP_CIPHER_gettable_ctx_params, EVP_CIPHER_CTX_gettable_params,
       EVP_CIPHER_CTX_set_params, EVP_CIPHER_settable_ctx_params,
       EVP_CIPHER_CTX_settable_params, EVP_CIPHER_CTX_get_block_size,
       EVP_CIPHER_CTX_get_key_length, EVP_CIPHER_CTX_get_iv_length,
       EVP_CIPHER_CTX_get_tag_length, EVP_CIPHER_CTX_get_app_data,
       EVP_CIPHER_CTX_set_app_data, EVP_CIPHER_CTX_flags,
       EVP_CIPHER_CTX_set_flags, EVP_CIPHER_CTX_clear_flags,
       EVP_CIPHER_CTX_test_flags, EVP_CIPHER_CTX_get_type,
       EVP_CIPHER_CTX_get_mode, EVP_CIPHER_CTX_get_num,
       EVP_CIPHER_CTX_set_num, EVP_CIPHER_CTX_is_encrypting,
       EVP_CIPHER_param_to_asn1, EVP_CIPHER_asn1_to_param,
       EVP_CIPHER_CTX_set_padding, EVP_enc_null, EVP_CIPHER_do_all_provided,
       EVP_CIPHER_nid, EVP_CIPHER_name, EVP_CIPHER_block_size,
       EVP_CIPHER_key_length, EVP_CIPHER_iv_length, EVP_CIPHER_flags,
       EVP_CIPHER_mode, EVP_CIPHER_type, EVP_CIPHER_CTX_encrypting,
       EVP_CIPHER_CTX_nid, EVP_CIPHER_CTX_block_size,
       EVP_CIPHER_CTX_key_length, EVP_CIPHER_CTX_iv_length,
       EVP_CIPHER_CTX_tag_length, EVP_CIPHER_CTX_num, EVP_CIPHER_CTX_type,
       EVP_CIPHER_CTX_mode - EVP cipher routines


SYNOPSIS

        #include <openssl/evp.h>

        EVP_CIPHER *EVP_CIPHER_fetch(OSSL_LIB_CTX *ctx, const char *algorithm,
                                     const char *properties);
        int EVP_CIPHER_up_ref(EVP_CIPHER *cipher);
        void EVP_CIPHER_free(EVP_CIPHER *cipher);
        EVP_CIPHER_CTX *EVP_CIPHER_CTX_new(void);
        int EVP_CIPHER_CTX_reset(EVP_CIPHER_CTX *ctx);
        void EVP_CIPHER_CTX_free(EVP_CIPHER_CTX *ctx);
        EVP_CIPHER_CTX *EVP_CIPHER_CTX_dup(const EVP_CIPHER_CTX *in);
        int EVP_CIPHER_CTX_copy(EVP_CIPHER_CTX *out, const EVP_CIPHER_CTX *in);

        int EVP_EncryptInit_ex(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
                               ENGINE *impl, const unsigned char *key, const unsigned char *iv);
        int EVP_EncryptInit_ex2(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
                                const unsigned char *key, const unsigned char *iv,
                                const OSSL_PARAM params[]);
        int EVP_EncryptUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
                              int *outl, const unsigned char *in, int inl);
        int EVP_EncryptFinal_ex(EVP_CIPHER_CTX *ctx, unsigned char *out, int *outl);

        int EVP_DecryptInit_ex(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
                               ENGINE *impl, const unsigned char *key, const unsigned char *iv);
        int EVP_DecryptInit_ex2(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
                                const unsigned char *key, const unsigned char *iv,
                                const OSSL_PARAM params[]);
        int EVP_DecryptUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
                              int *outl, const unsigned char *in, int inl);
        int EVP_DecryptFinal_ex(EVP_CIPHER_CTX *ctx, unsigned char *outm, int *outl);

        int EVP_CipherInit_ex(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
                              ENGINE *impl, const unsigned char *key, const unsigned char *iv, int enc);
        int EVP_CipherInit_ex2(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
                               const unsigned char *key, const unsigned char *iv,
                               int enc, const OSSL_PARAM params[]);
        int EVP_CipherUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
                             int *outl, const unsigned char *in, int inl);
        int EVP_CipherFinal_ex(EVP_CIPHER_CTX *ctx, unsigned char *outm, int *outl);

        int EVP_EncryptInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
                            const unsigned char *key, const unsigned char *iv);
        int EVP_EncryptFinal(EVP_CIPHER_CTX *ctx, unsigned char *out, int *outl);

        int EVP_DecryptInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
                            const unsigned char *key, const unsigned char *iv);
        int EVP_DecryptFinal(EVP_CIPHER_CTX *ctx, unsigned char *outm, int *outl);

        int EVP_CipherInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
                           const unsigned char *key, const unsigned char *iv, int enc);
        int EVP_CipherFinal(EVP_CIPHER_CTX *ctx, unsigned char *outm, int *outl);

        int EVP_Cipher(EVP_CIPHER_CTX *ctx, unsigned char *out,
                       const unsigned char *in, unsigned int inl);

        int EVP_CIPHER_CTX_set_padding(EVP_CIPHER_CTX *x, int padding);
        int EVP_CIPHER_CTX_set_key_length(EVP_CIPHER_CTX *x, int keylen);
        int EVP_CIPHER_CTX_ctrl(EVP_CIPHER_CTX *ctx, int cmd, int p1, void *p2);
        int EVP_CIPHER_CTX_rand_key(EVP_CIPHER_CTX *ctx, unsigned char *key);
        void EVP_CIPHER_CTX_set_flags(EVP_CIPHER_CTX *ctx, int flags);
        void EVP_CIPHER_CTX_clear_flags(EVP_CIPHER_CTX *ctx, int flags);
        int EVP_CIPHER_CTX_test_flags(const EVP_CIPHER_CTX *ctx, int flags);

        const EVP_CIPHER *EVP_get_cipherbyname(const char *name);
        const EVP_CIPHER *EVP_get_cipherbynid(int nid);
        const EVP_CIPHER *EVP_get_cipherbyobj(const ASN1_OBJECT *a);

        int EVP_CIPHER_get_nid(const EVP_CIPHER *e);
        int EVP_CIPHER_is_a(const EVP_CIPHER *cipher, const char *name);
        int EVP_CIPHER_names_do_all(const EVP_CIPHER *cipher,
                                    void (*fn)(const char *name, void *data),
                                    void *data);
        const char *EVP_CIPHER_get0_name(const EVP_CIPHER *cipher);
        const char *EVP_CIPHER_get0_description(const EVP_CIPHER *cipher);
        const OSSL_PROVIDER *EVP_CIPHER_get0_provider(const EVP_CIPHER *cipher);
        int EVP_CIPHER_get_block_size(const EVP_CIPHER *e);
        int EVP_CIPHER_get_key_length(const EVP_CIPHER *e);
        int EVP_CIPHER_get_iv_length(const EVP_CIPHER *e);
        unsigned long EVP_CIPHER_get_flags(const EVP_CIPHER *e);
        unsigned long EVP_CIPHER_get_mode(const EVP_CIPHER *e);
        int EVP_CIPHER_get_type(const EVP_CIPHER *cipher);

        const EVP_CIPHER *EVP_CIPHER_CTX_get0_cipher(const EVP_CIPHER_CTX *ctx);
        EVP_CIPHER *EVP_CIPHER_CTX_get1_cipher(const EVP_CIPHER_CTX *ctx);
        int EVP_CIPHER_CTX_get_nid(const EVP_CIPHER_CTX *ctx);
        const char *EVP_CIPHER_CTX_get0_name(const EVP_CIPHER_CTX *ctx);

        int EVP_CIPHER_get_params(EVP_CIPHER *cipher, OSSL_PARAM params[]);
        int EVP_CIPHER_CTX_set_params(EVP_CIPHER_CTX *ctx, const OSSL_PARAM params[]);
        int EVP_CIPHER_CTX_get_params(EVP_CIPHER_CTX *ctx, OSSL_PARAM params[]);
        const OSSL_PARAM *EVP_CIPHER_gettable_params(const EVP_CIPHER *cipher);
        const OSSL_PARAM *EVP_CIPHER_settable_ctx_params(const EVP_CIPHER *cipher);
        const OSSL_PARAM *EVP_CIPHER_gettable_ctx_params(const EVP_CIPHER *cipher);
        const OSSL_PARAM *EVP_CIPHER_CTX_settable_params(EVP_CIPHER_CTX *ctx);
        const OSSL_PARAM *EVP_CIPHER_CTX_gettable_params(EVP_CIPHER_CTX *ctx);
        int EVP_CIPHER_CTX_get_block_size(const EVP_CIPHER_CTX *ctx);
        int EVP_CIPHER_CTX_get_key_length(const EVP_CIPHER_CTX *ctx);
        int EVP_CIPHER_CTX_get_iv_length(const EVP_CIPHER_CTX *ctx);
        int EVP_CIPHER_CTX_get_tag_length(const EVP_CIPHER_CTX *ctx);
        void *EVP_CIPHER_CTX_get_app_data(const EVP_CIPHER_CTX *ctx);
        void EVP_CIPHER_CTX_set_app_data(const EVP_CIPHER_CTX *ctx, void *data);
        int EVP_CIPHER_CTX_get_type(const EVP_CIPHER_CTX *ctx);
        int EVP_CIPHER_CTX_get_mode(const EVP_CIPHER_CTX *ctx);
        int EVP_CIPHER_CTX_get_num(const EVP_CIPHER_CTX *ctx);
        int EVP_CIPHER_CTX_set_num(EVP_CIPHER_CTX *ctx, int num);
        int EVP_CIPHER_CTX_is_encrypting(const EVP_CIPHER_CTX *ctx);

        int EVP_CIPHER_param_to_asn1(EVP_CIPHER_CTX *c, ASN1_TYPE *type);
        int EVP_CIPHER_asn1_to_param(EVP_CIPHER_CTX *c, ASN1_TYPE *type);

        void EVP_CIPHER_do_all_provided(OSSL_LIB_CTX *libctx,
                                        void (*fn)(EVP_CIPHER *cipher, void *arg),
                                        void *arg);

        #define EVP_CIPHER_nid EVP_CIPHER_get_nid
        #define EVP_CIPHER_name EVP_CIPHER_get0_name
        #define EVP_CIPHER_block_size EVP_CIPHER_get_block_size
        #define EVP_CIPHER_key_length EVP_CIPHER_get_key_length
        #define EVP_CIPHER_iv_length EVP_CIPHER_get_iv_length
        #define EVP_CIPHER_flags EVP_CIPHER_get_flags
        #define EVP_CIPHER_mode EVP_CIPHER_get_mode
        #define EVP_CIPHER_type EVP_CIPHER_get_type
        #define EVP_CIPHER_CTX_encrypting EVP_CIPHER_CTX_is_encrypting
        #define EVP_CIPHER_CTX_nid EVP_CIPHER_CTX_get_nid
        #define EVP_CIPHER_CTX_block_size EVP_CIPHER_CTX_get_block_size
        #define EVP_CIPHER_CTX_key_length EVP_CIPHER_CTX_get_key_length
        #define EVP_CIPHER_CTX_iv_length EVP_CIPHER_CTX_get_iv_length
        #define EVP_CIPHER_CTX_tag_length EVP_CIPHER_CTX_get_tag_length
        #define EVP_CIPHER_CTX_num EVP_CIPHER_CTX_get_num
        #define EVP_CIPHER_CTX_type EVP_CIPHER_CTX_get_type
        #define EVP_CIPHER_CTX_mode EVP_CIPHER_CTX_get_mode

       The following function has been deprecated since OpenSSL 3.0, and can
       be hidden entirely by defining OPENSSL_API_COMPAT with a suitable
       version value, see openssl_user_macros(7):

        const EVP_CIPHER *EVP_CIPHER_CTX_cipher(const EVP_CIPHER_CTX *ctx);

       The following function has been deprecated since OpenSSL 1.1.0, and can
       be hidden entirely by defining OPENSSL_API_COMPAT with a suitable
       version value, see openssl_user_macros(7):

        int EVP_CIPHER_CTX_flags(const EVP_CIPHER_CTX *ctx);


DESCRIPTION

       The EVP cipher routines are a high-level interface to certain symmetric
       ciphers.

       The EVP_CIPHER type is a structure for cipher method implementation.

       EVP_CIPHER_fetch()
           Fetches the cipher implementation for the given algorithm from any
           provider offering it, within the criteria given by the properties.
           See "ALGORITHM FETCHING" in crypto(7) for further information.

           The returned value must eventually be freed with EVP_CIPHER_free().

           Fetched EVP_CIPHER structures are reference counted.

       EVP_CIPHER_up_ref()
           Increments the reference count for an EVP_CIPHER structure.

       EVP_CIPHER_free()
           Decrements the reference count for the fetched EVP_CIPHER
           structure.  If the reference count drops to 0 then the structure is
           freed.

       EVP_CIPHER_CTX_new()
           Allocates and returns a cipher context.

       EVP_CIPHER_CTX_free()
           Clears all information from a cipher context and frees any
           allocated memory associated with it, including ctx itself. This
           function should be called after all operations using a cipher are
           complete so sensitive information does not remain in memory.

       EVP_CIPHER_CTX_dup()
           Can be used to duplicate the cipher state from in.  This is useful
           to avoid multiple EVP_MD_fetch() calls or if large amounts of data
           are to be hashed which only differ in the last few bytes.

       EVP_CIPHER_CTX_copy()
           Can be used to copy the cipher state from in to out.

       EVP_CIPHER_CTX_ctrl()
           This is a legacy method. EVP_CIPHER_CTX_set_params() and
           EVP_CIPHER_CTX_get_params() is the mechanism that should be used to
           set and get parameters that are used by providers.

           Performs cipher-specific control actions on context ctx. The
           control command is indicated in cmd and any additional arguments in
           p1 and p2.  EVP_CIPHER_CTX_ctrl() must be called after
           EVP_CipherInit_ex2(). Other restrictions may apply depending on the
           control type and cipher implementation.

           If this function happens to be used with a fetched EVP_CIPHER, it
           will translate the controls that are known to OpenSSL into
           OSSL_PARAM(3) parameters with keys defined by OpenSSL and call
           EVP_CIPHER_CTX_get_params() or EVP_CIPHER_CTX_set_params() as is
           appropriate for each control command.

           See "CONTROLS" below for more information, including what
           translations are being done.

       EVP_CIPHER_get_params()
           Retrieves the requested list of algorithm params from a CIPHER
           cipher.  See "PARAMETERS" below for more information.

       EVP_CIPHER_CTX_get_params()
           Retrieves the requested list of params from CIPHER context ctx.
           See "PARAMETERS" below for more information.

       EVP_CIPHER_CTX_set_params()
           Sets the list of params into a CIPHER context ctx.  See
           "PARAMETERS" below for more information.

       EVP_CIPHER_gettable_params()
           Get a constant OSSL_PARAM(3) array that describes the retrievable
           parameters that can be used with EVP_CIPHER_get_params().

       EVP_CIPHER_gettable_ctx_params() and EVP_CIPHER_CTX_gettable_params()
           Get a constant OSSL_PARAM(3) array that describes the retrievable
           parameters that can be used with EVP_CIPHER_CTX_get_params().
           EVP_CIPHER_gettable_ctx_params() returns the parameters that can be
           retrieved from the algorithm, whereas
           EVP_CIPHER_CTX_gettable_params() returns the parameters that can be
           retrieved in the context's current state.

       EVP_CIPHER_settable_ctx_params() and EVP_CIPHER_CTX_settable_params()
           Get a constant OSSL_PARAM(3) array that describes the settable
           parameters that can be used with EVP_CIPHER_CTX_set_params().
           EVP_CIPHER_settable_ctx_params() returns the parameters that can be
           set from the algorithm, whereas EVP_CIPHER_CTX_settable_params()
           returns the parameters that can be set in the context's current
           state.

       EVP_EncryptInit_ex2()
           Sets up cipher context ctx for encryption with cipher type. type is
           typically supplied by calling EVP_CIPHER_fetch(). type may also be
           set using legacy functions such as EVP_aes_256_cbc(), but this is
           not recommended for new applications. key is the symmetric key to
           use and iv is the IV to use (if necessary), the actual number of
           bytes used for the key and IV depends on the cipher. The parameters
           params will be set on the context after initialisation. It is
           possible to set all parameters to NULL except type in an initial
           call and supply the remaining parameters in subsequent calls, all
           of which have type set to NULL. This is done when the default
           cipher parameters are not appropriate.  For EVP_CIPH_GCM_MODE the
           IV will be generated internally if it is not specified.

       EVP_EncryptInit_ex()
           This legacy function is similar to EVP_EncryptInit_ex2() when impl
           is NULL. The implementation of the type from the impl engine will
           be used if it exists.

       EVP_EncryptUpdate()
           Encrypts inl bytes from the buffer in and writes the encrypted
           version to out. This function can be called multiple times to
           encrypt successive blocks of data. The amount of data written
           depends on the block alignment of the encrypted data.  For most
           ciphers and modes, the amount of data written can be anything from
           zero bytes to (inl + cipher_block_size - 1) bytes.  For wrap cipher
           modes, the amount of data written can be anything from zero bytes
           to (inl + cipher_block_size) bytes.  For stream ciphers, the amount
           of data written can be anything from zero bytes to inl bytes.
           Thus, out should contain sufficient room for the operation being
           performed.  The actual number of bytes written is placed in outl.
           It also checks if in and out are partially overlapping, and if they
           are 0 is returned to indicate failure.

           If padding is enabled (the default) then EVP_EncryptFinal_ex()
           encrypts the "final" data, that is any data that remains in a
           partial block.  It uses standard block padding (aka PKCS padding)
           as described in the NOTES section, below. The encrypted final data
           is written to out which should have sufficient space for one cipher
           block. The number of bytes written is placed in outl. After this
           function is called the encryption operation is finished and no
           further calls to EVP_EncryptUpdate() should be made.

           If padding is disabled then EVP_EncryptFinal_ex() will not encrypt
           any more data and it will return an error if any data remains in a
           partial block: that is if the total data length is not a multiple
           of the block size.

       EVP_DecryptInit_ex2(), EVP_DecryptInit_ex(), EVP_DecryptUpdate() and
       EVP_DecryptFinal_ex()
           These functions are the corresponding decryption operations.
           EVP_DecryptFinal() will return an error code if padding is enabled
           and the final block is not correctly formatted. The parameters and
           restrictions are identical to the encryption operations except that
           if padding is enabled the decrypted data buffer out passed to
           EVP_DecryptUpdate() should have sufficient room for (inl +
           cipher_block_size) bytes unless the cipher block size is 1 in which
           case inl bytes is sufficient.

       EVP_CipherInit_ex2(), EVP_CipherInit_ex(), EVP_CipherUpdate() and
       EVP_CipherFinal_ex()
           These functions can be used for decryption or encryption. The
           operation performed depends on the value of the enc parameter. It
           should be set to 1 for encryption, 0 for decryption and -1 to leave
           the value unchanged (the actual value of 'enc' being supplied in a
           previous call).

       EVP_CIPHER_CTX_reset()
           Clears all information from a cipher context and free up any
           allocated memory associated with it, except the ctx itself. This
           function should be called anytime ctx is reused by another
           EVP_CipherInit() / EVP_CipherUpdate() / EVP_CipherFinal() series of
           calls.

       EVP_EncryptInit(3), EVP_DecryptInit() and EVP_CipherInit()
           Behave in a similar way to EVP_EncryptInit_ex(),
           EVP_DecryptInit_ex() and EVP_CipherInit_ex() except if the type is
           not a fetched cipher they use the default implementation of the
           type.

       EVP_EncryptFinal(), EVP_DecryptFinal() and EVP_CipherFinal()
           Identical to EVP_EncryptFinal_ex(), EVP_DecryptFinal_ex() and
           EVP_CipherFinal_ex(). In previous releases they also cleaned up the
           ctx, but this is no longer done and EVP_CIPHER_CTX_cleanup() must
           be called to free any context resources.

       EVP_Cipher()
           Encrypts or decrypts a maximum inl amount of bytes from in and
           leaves the result in out.

           For legacy ciphers - If the cipher doesn't have the flag
           EVP_CIPH_FLAG_CUSTOM_CIPHER set, then inl must be a multiple of
           EVP_CIPHER_get_block_size().  If it isn't, the result is undefined.
           If the cipher has that flag set, then inl can be any size.

           Due to the constraints of the API contract of this function it
           shouldn't be used in applications, please consider using
           EVP_CipherUpdate() and EVP_CipherFinal_ex() instead.

       EVP_get_cipherbyname(), EVP_get_cipherbynid() and EVP_get_cipherbyobj()
           Returns an EVP_CIPHER structure when passed a cipher name, a cipher
           NID or an ASN1_OBJECT structure respectively.

           EVP_get_cipherbyname() will return NULL for algorithms such as
           "AES-128-SIV", "AES-128-CBC-CTS" and "CAMELLIA-128-CBC-CTS" which
           were previously only accessible via low level interfaces.

           The EVP_get_cipherbyname() function is present for backwards
           compatibility with OpenSSL prior to version 3 and is different to
           the EVP_CIPHER_fetch() function since it does not attempt to
           "fetch" an implementation of the cipher.  Additionally, it only
           knows about ciphers that are built-in to OpenSSL and have an
           associated NID. Similarly EVP_get_cipherbynid() and
           EVP_get_cipherbyobj() also return objects without an associated
           implementation.

           When the cipher objects returned by these functions are used (such
           as in a call to EVP_EncryptInit_ex()) an implementation of the
           cipher will be implicitly fetched from the loaded providers. This
           fetch could fail if no suitable implementation is available. Use
           EVP_CIPHER_fetch() instead to explicitly fetch the algorithm and an
           associated implementation from a provider.

           See "ALGORITHM FETCHING" in crypto(7) for more information about
           fetching.

           The cipher objects returned from these functions do not need to be
           freed with EVP_CIPHER_free().

       EVP_CIPHER_get_nid() and EVP_CIPHER_CTX_get_nid()
           Return the NID of a cipher when passed an EVP_CIPHER or
           EVP_CIPHER_CTX structure.  The actual NID value is an internal
           value which may not have a corresponding OBJECT IDENTIFIER.

       EVP_CIPHER_CTX_set_flags(), EVP_CIPHER_CTX_clear_flags() and
       EVP_CIPHER_CTX_test_flags()
           Sets, clears and tests ctx flags.  See "FLAGS" below for more
           information.

           For provided ciphers EVP_CIPHER_CTX_set_flags() should be called
           only after the fetched cipher has been assigned to the ctx. It is
           recommended to use "PARAMETERS" instead.

       EVP_CIPHER_CTX_set_padding()
           Enables or disables padding. This function should be called after
           the context is set up for encryption or decryption with
           EVP_EncryptInit_ex2(), EVP_DecryptInit_ex2() or
           EVP_CipherInit_ex2(). By default encryption operations are padded
           using standard block padding and the padding is checked and removed
           when decrypting. If the pad parameter is zero then no padding is
           performed, the total amount of data encrypted or decrypted must
           then be a multiple of the block size or an error will occur.

       EVP_CIPHER_get_key_length() and EVP_CIPHER_CTX_get_key_length()
           Return the key length of a cipher when passed an EVP_CIPHER or
           EVP_CIPHER_CTX structure. The constant EVP_MAX_KEY_LENGTH is the
           maximum key length for all ciphers. Note: although
           EVP_CIPHER_get_key_length() is fixed for a given cipher, the value
           of EVP_CIPHER_CTX_get_key_length() may be different for variable
           key length ciphers.

       EVP_CIPHER_CTX_set_key_length()
           Sets the key length of the cipher context.  If the cipher is a
           fixed length cipher then attempting to set the key length to any
           value other than the fixed value is an error.

       EVP_CIPHER_get_iv_length() and EVP_CIPHER_CTX_get_iv_length()
           Return the IV length of a cipher when passed an EVP_CIPHER or
           EVP_CIPHER_CTX. It will return zero if the cipher does not use an
           IV. The constant EVP_MAX_IV_LENGTH is the maximum IV length for all
           ciphers.

       EVP_CIPHER_CTX_get_tag_length()
           Returns the tag length of an AEAD cipher when passed a
           EVP_CIPHER_CTX. It will return zero if the cipher does not support
           a tag. It returns a default value if the tag length has not been
           set.

       EVP_CIPHER_get_block_size() and EVP_CIPHER_CTX_get_block_size()
           Return the block size of a cipher when passed an EVP_CIPHER or
           EVP_CIPHER_CTX structure. The constant EVP_MAX_BLOCK_LENGTH is also
           the maximum block length for all ciphers.

       EVP_CIPHER_get_type() and EVP_CIPHER_CTX_get_type()
           Return the type of the passed cipher or context. This "type" is the
           actual NID of the cipher OBJECT IDENTIFIER and as such it ignores
           the cipher parameters (40 bit RC2 and 128 bit RC2 have the same
           NID). If the cipher does not have an object identifier or does not
           have ASN1 support this function will return NID_undef.

       EVP_CIPHER_is_a()
           Returns 1 if cipher is an implementation of an algorithm that's
           identifiable with name, otherwise 0. If cipher is a legacy cipher
           (it's the return value from the likes of EVP_aes128() rather than
           the result of an EVP_CIPHER_fetch()), only cipher names registered
           with the default library context (see OSSL_LIB_CTX(3)) will be
           considered.

       EVP_CIPHER_get0_name() and EVP_CIPHER_CTX_get0_name()
           Return the name of the passed cipher or context.  For fetched
           ciphers with multiple names, only one of them is returned. See also
           EVP_CIPHER_names_do_all().

       EVP_CIPHER_names_do_all()
           Traverses all names for the cipher, and calls fn with each name and
           data.  This is only useful with fetched EVP_CIPHERs.

       EVP_CIPHER_get0_description()
           Returns a description of the cipher, meant for display and human
           consumption.  The description is at the discretion of the cipher
           implementation.

       EVP_CIPHER_get0_provider()
           Returns an OSSL_PROVIDER pointer to the provider that implements
           the given EVP_CIPHER.

       EVP_CIPHER_CTX_get0_cipher()
           Returns the EVP_CIPHER structure when passed an EVP_CIPHER_CTX
           structure.  EVP_CIPHER_CTX_get1_cipher() is the same except the
           ownership is passed to the caller.

       EVP_CIPHER_get_mode() and EVP_CIPHER_CTX_get_mode()
           Return the block cipher mode: EVP_CIPH_ECB_MODE, EVP_CIPH_CBC_MODE,
           EVP_CIPH_CFB_MODE, EVP_CIPH_OFB_MODE, EVP_CIPH_CTR_MODE,
           EVP_CIPH_GCM_MODE, EVP_CIPH_CCM_MODE, EVP_CIPH_XTS_MODE,
           EVP_CIPH_WRAP_MODE, EVP_CIPH_OCB_MODE or EVP_CIPH_SIV_MODE. If the
           cipher is a stream cipher then EVP_CIPH_STREAM_CIPHER is returned.

       EVP_CIPHER_get_flags()
           Returns any flags associated with the cipher. See "FLAGS" for a
           list of currently defined flags.

       EVP_CIPHER_CTX_get_num() and EVP_CIPHER_CTX_set_num()
           Gets or sets the cipher specific "num" parameter for the associated
           ctx.  Built-in ciphers typically use this to track how much of the
           current underlying block has been "used" already.

       EVP_CIPHER_CTX_is_encrypting()
           Reports whether the ctx is being used for encryption or decryption.

       EVP_CIPHER_CTX_flags()
           A deprecated macro calling
           "EVP_CIPHER_get_flags(EVP_CIPHER_CTX_get0_cipher(ctx))".  Do not
           use.

       EVP_CIPHER_param_to_asn1()
           Sets the AlgorithmIdentifier "parameter" based on the passed
           cipher. This will typically include any parameters and an IV. The
           cipher IV (if any) must be set when this call is made. This call
           should be made before the cipher is actually "used" (before any
           EVP_EncryptUpdate(), EVP_DecryptUpdate() calls for example).  This
           function may fail if the cipher does not have any ASN1 support.

       EVP_CIPHER_asn1_to_param()
           Sets the cipher parameters based on an ASN1 AlgorithmIdentifier
           "parameter".  The precise effect depends on the cipher. In the case
           of RC2, for example, it will set the IV and effective key length.
           This function should be called after the base cipher type is set
           but before the key is set. For example EVP_CipherInit() will be
           called with the IV and key set to NULL, EVP_CIPHER_asn1_to_param()
           will be called and finally EVP_CipherInit() again with all
           parameters except the key set to NULL. It is possible for this
           function to fail if the cipher does not have any ASN1 support or
           the parameters cannot be set (for example the RC2 effective key
           length is not supported.

       EVP_CIPHER_CTX_rand_key()
           Generates a random key of the appropriate length based on the
           cipher context.  The EVP_CIPHER can provide its own random key
           generation routine to support keys of a specific form. key must
           point to a buffer at least as big as the value returned by
           EVP_CIPHER_CTX_get_key_length().

       EVP_CIPHER_do_all_provided()
           Traverses all ciphers implemented by all activated providers in the
           given library context libctx, and for each of the implementations,
           calls the given function fn with the implementation method and the
           given arg as argument.


PARAMETERS

       See OSSL_PARAM(3) for information about passing parameters.

   Gettable EVP_CIPHER parameters
       When EVP_CIPHER_fetch() is called it internally calls
       EVP_CIPHER_get_params() and caches the results.

       EVP_CIPHER_get_params() can be used with the following OSSL_PARAM(3)
       keys:

       "mode" (OSSL_CIPHER_PARAM_MODE) <unsigned integer>
           Gets the mode for the associated cipher algorithm cipher.  See
           "EVP_CIPHER_get_mode() and EVP_CIPHER_CTX_get_mode()" for a list of
           valid modes.  Use EVP_CIPHER_get_mode() to retrieve the cached
           value.

       "keylen" (OSSL_CIPHER_PARAM_KEYLEN) <unsigned integer>
           Gets the key length for the associated cipher algorithm cipher.
           Use EVP_CIPHER_get_key_length() to retrieve the cached value.

       "ivlen" (OSSL_CIPHER_PARAM_IVLEN) <unsigned integer>
           Gets the IV length for the associated cipher algorithm cipher.  Use
           EVP_CIPHER_get_iv_length() to retrieve the cached value.

       "blocksize" (OSSL_CIPHER_PARAM_BLOCK_SIZE) <unsigned integer>
           Gets the block size for the associated cipher algorithm cipher.
           The block size should be 1 for stream ciphers.  Note that the block
           size for a cipher may be different to the block size for the
           underlying encryption/decryption primitive.  For example AES in CTR
           mode has a block size of 1 (because it operates like a stream
           cipher), even though AES has a block size of 16.  Use
           EVP_CIPHER_get_block_size() to retrieve the cached value.

       "aead" (OSSL_CIPHER_PARAM_AEAD) <integer>
           Gets 1 if this is an AEAD cipher algorithm, otherwise it gets 0.
           Use (EVP_CIPHER_get_flags(cipher) & EVP_CIPH_FLAG_AEAD_CIPHER) to
           retrieve the cached value.

       "custom-iv" (OSSL_CIPHER_PARAM_CUSTOM_IV) <integer>
           Gets 1 if the cipher algorithm cipher has a custom IV, otherwise it
           gets 0.  Storing and initializing the IV is left entirely to the
           implementation, if a custom IV is used.  Use
           (EVP_CIPHER_get_flags(cipher) & EVP_CIPH_CUSTOM_IV) to retrieve the
           cached value.

       "cts" (OSSL_CIPHER_PARAM_CTS) <integer>
           Gets 1 if the cipher algorithm cipher uses ciphertext stealing,
           otherwise it gets 0.  This is currently used to indicate that the
           cipher is a one shot that only allows a single call to
           EVP_CipherUpdate().  Use (EVP_CIPHER_get_flags(cipher) &
           EVP_CIPH_FLAG_CTS) to retrieve the cached value.

       "tls-multi" (OSSL_CIPHER_PARAM_TLS1_MULTIBLOCK) <integer>
           Gets 1 if the cipher algorithm cipher supports interleaving of
           crypto blocks, otherwise it gets 0. The interleaving is an
           optimization only applicable to certain TLS ciphers.  Use
           (EVP_CIPHER_get_flags(cipher) & EVP_CIPH_FLAG_TLS1_1_MULTIBLOCK) to
           retrieve the cached value.

       "has-randkey" (OSSL_CIPHER_PARAM_HAS_RANDKEY) <integer>
           Gets 1 if the cipher algorithm cipher supports the gettable
           EVP_CIPHER_CTX parameter OSSL_CIPHER_PARAM_RANDOM_KEY. Only DES and
           3DES set this to 1, all other OpenSSL ciphers return 0.

   Gettable and Settable EVP_CIPHER_CTX parameters
       The following OSSL_PARAM(3) keys can be used with both
       EVP_CIPHER_CTX_get_params() and EVP_CIPHER_CTX_set_params().

       "padding" (OSSL_CIPHER_PARAM_PADDING) <unsigned integer>
           Gets or sets the padding mode for the cipher context ctx.  Padding
           is enabled if the value is 1, and disabled if the value is 0.  See
           also EVP_CIPHER_CTX_set_padding().

       "num" (OSSL_CIPHER_PARAM_NUM) <unsigned integer>
           Gets or sets the cipher specific "num" parameter for the cipher
           context ctx.  Built-in ciphers typically use this to track how much
           of the current underlying block has been "used" already.  See also
           EVP_CIPHER_CTX_get_num() and EVP_CIPHER_CTX_set_num().

       "keylen" (OSSL_CIPHER_PARAM_KEYLEN) <unsigned integer>
           Gets or sets the key length for the cipher context ctx.  The length
           of the "keylen" parameter should not exceed that of a size_t.  See
           also EVP_CIPHER_CTX_get_key_length() and
           EVP_CIPHER_CTX_set_key_length().

       "tag" (OSSL_CIPHER_PARAM_AEAD_TAG) <octet string>
           Gets or sets the AEAD tag for the associated cipher context ctx.
           See "AEAD Interface" in EVP_EncryptInit(3).

       "keybits" (OSSL_CIPHER_PARAM_RC2_KEYBITS) <unsigned integer>
           Gets or sets the effective keybits used for a RC2 cipher.  The
           length of the "keybits" parameter should not exceed that of a
           size_t.

       "rounds" (OSSL_CIPHER_PARAM_ROUNDS) <unsigned integer>
           Gets or sets the number of rounds to be used for a cipher.  This is
           used by the RC5 cipher.

       "alg_id_param" (OSSL_CIPHER_PARAM_ALGORITHM_ID_PARAMS) <octet string>
           Used to pass the DER encoded AlgorithmIdentifier parameter to or
           from the cipher implementation.  Functions like
           EVP_CIPHER_param_to_asn1(3) and EVP_CIPHER_asn1_to_param(3) use
           this parameter for any implementation that has the flag
           EVP_CIPH_FLAG_CUSTOM_ASN1 set.

       "cts_mode" (OSSL_CIPHER_PARAM_CTS_MODE) <UTF8 string>
           Gets or sets the cipher text stealing mode. For all modes the
           output size is the same as the input size. The input length must be
           greater than or equal to the block size. (The block size for AES
           and CAMELLIA is 16 bytes).

           Valid values for the mode are:

           "CS1"
               The NIST variant of cipher text stealing.  For input lengths
               that are multiples of the block size it is equivalent to using
               a "AES-XXX-CBC" or "CAMELLIA-XXX-CBC" cipher otherwise the
               second last cipher text block is a partial block.

           "CS2"
               For input lengths that are multiples of the block size it is
               equivalent to using a "AES-XXX-CBC" or "CAMELLIA-XXX-CBC"
               cipher, otherwise it is the same as "CS3" mode.

           "CS3"
               The Kerberos5 variant of cipher text stealing which always
               swaps the last cipher text block with the previous block (which
               may be a partial or full block depending on the input length).
               If the input length is exactly one full block then this is
               equivalent to using a "AES-XXX-CBC" or "CAMELLIA-XXX-CBC"
               cipher.

           The default is "CS1". This is only supported for "AES-128-CBC-CTS",
           "AES-192-CBC-CTS", "AES-256-CBC-CTS", "CAMELLIA-128-CBC-CTS",
           "CAMELLIA-192-CBC-CTS" and "CAMELLIA-256-CBC-CTS".

       "tls1multi_interleave" (OSSL_CIPHER_PARAM_TLS1_MULTIBLOCK_INTERLEAVE)
       <unsigned integer>
           Sets or gets the number of records being sent in one go for a tls1
           multiblock cipher operation (either 4 or 8 records).

   Gettable EVP_CIPHER_CTX parameters
       The following OSSL_PARAM(3) keys can be used with
       EVP_CIPHER_CTX_get_params():

       "ivlen" (OSSL_CIPHER_PARAM_IVLEN and <OSSL_CIPHER_PARAM_AEAD_IVLEN)
       <unsigned integer>
           Gets the IV length for the cipher context ctx.  The length of the
           "ivlen" parameter should not exceed that of a size_t.  See also
           EVP_CIPHER_CTX_get_iv_length().

       "iv" (OSSL_CIPHER_PARAM_IV) <octet string OR octet ptr>
           Gets the IV used to initialize the associated cipher context ctx.
           See also EVP_CIPHER_CTX_get_original_iv().

       "updated-iv" (OSSL_CIPHER_PARAM_UPDATED_IV) <octet string OR octet ptr>
           Gets the updated pseudo-IV state for the associated cipher context,
           e.g., the previous ciphertext block for CBC mode or the iteratively
           encrypted IV value for OFB mode.  Note that octet pointer access is
           deprecated and is provided only for backwards compatibility with
           historical libcrypto APIs.  See also
           EVP_CIPHER_CTX_get_updated_iv().

       "randkey" (OSSL_CIPHER_PARAM_RANDOM_KEY) <octet string>
           Gets an implementation specific randomly generated key for the
           associated cipher context ctx. This is currently only supported by
           DES and 3DES (which set the key to odd parity).

       "taglen" (OSSL_CIPHER_PARAM_AEAD_TAGLEN) <unsigned integer>
           Gets the tag length to be used for an AEAD cipher for the
           associated cipher context ctx. It gets a default value if it has
           not been set.  The length of the "taglen" parameter should not
           exceed that of a size_t.  See also EVP_CIPHER_CTX_get_tag_length().

       "tlsaadpad" (OSSL_CIPHER_PARAM_AEAD_TLS1_AAD_PAD) <unsigned integer>
           Gets the length of the tag that will be added to a TLS record for
           the AEAD tag for the associated cipher context ctx.  The length of
           the "tlsaadpad" parameter should not exceed that of a size_t.

       "tlsivgen" (OSSL_CIPHER_PARAM_AEAD_TLS1_GET_IV_GEN) <octet string>
           Gets the invocation field generated for encryption.  Can only be
           called after "tlsivfixed" is set.  This is only used for GCM mode.

       "tls1multi_enclen" (OSSL_CIPHER_PARAM_TLS1_MULTIBLOCK_ENC_LEN)
       <unsigned integer>
           Get the total length of the record returned from the
           "tls1multi_enc" operation.

       "tls1multi_maxbufsz" (OSSL_CIPHER_PARAM_TLS1_MULTIBLOCK_MAX_BUFSIZE)
       <unsigned integer>
           Gets the maximum record length for a TLS1 multiblock cipher
           operation.  The length of the "tls1multi_maxbufsz" parameter should
           not exceed that of a size_t.

       "tls1multi_aadpacklen" (OSSL_CIPHER_PARAM_TLS1_MULTIBLOCK_AAD_PACKLEN)
       <unsigned integer>
           Gets the result of running the "tls1multi_aad" operation.

       "tls-mac" (OSSL_CIPHER_PARAM_TLS_MAC) <octet ptr>
           Used to pass the TLS MAC data.

   Settable EVP_CIPHER_CTX parameters
       The following OSSL_PARAM(3) keys can be used with
       EVP_CIPHER_CTX_set_params():

       "mackey" (OSSL_CIPHER_PARAM_AEAD_MAC_KEY) <octet string>
           Sets the MAC key used by composite AEAD ciphers such as
           AES-CBC-HMAC-SHA256.

       "speed" (OSSL_CIPHER_PARAM_SPEED) <unsigned integer>
           Sets the speed option for the associated cipher context. This is
           only supported by AES SIV ciphers which disallow multiple
           operations by default.  Setting "speed" to 1 allows another encrypt
           or decrypt operation to be performed. This is used for performance
           testing.

       "use-bits" (OSSL_CIPHER_PARAM_USE_BITS) <unsigned integer>
           Determines if the input length inl passed to EVP_EncryptUpdate(),
           EVP_DecryptUpdate() and EVP_CipherUpdate() is the number of bits or
           number of bytes.  Setting "use-bits" to 1 uses bits. The default is
           in bytes.  This is only used for CFB1 ciphers.

           This can be set using EVP_CIPHER_CTX_set_flags(ctx,
           EVP_CIPH_FLAG_LENGTH_BITS).

       "tls-version" (OSSL_CIPHER_PARAM_TLS_VERSION) <integer>
           Sets the TLS version.

       "tls-mac-size" (OSSL_CIPHER_PARAM_TLS_MAC_SIZE) <unsigned integer>
           Set the TLS MAC size.

       "tlsaad" (OSSL_CIPHER_PARAM_AEAD_TLS1_AAD) <octet string>
           Sets TLSv1.2 AAD information for the associated cipher context ctx.
           TLSv1.2 AAD information is always 13 bytes in length and is as
           defined for the "additional_data" field described in section
           6.2.3.3 of RFC5246.

       "tlsivfixed" (OSSL_CIPHER_PARAM_AEAD_TLS1_IV_FIXED) <octet string>
           Sets the fixed portion of an IV for an AEAD cipher used in a TLS
           record encryption/ decryption for the associated cipher context.
           TLS record encryption/decryption always occurs "in place" so that
           the input and output buffers are always the same memory location.
           AEAD IVs in TLSv1.2 consist of an implicit "fixed" part and an
           explicit part that varies with every record.  Setting a TLS fixed
           IV changes a cipher to encrypt/decrypt TLS records.  TLS records
           are encrypted/decrypted using a single OSSL_FUNC_cipher_cipher call
           per record.  For a record decryption the first bytes of the input
           buffer will be the explicit part of the IV and the final bytes of
           the input buffer will be the AEAD tag.  The length of the explicit
           part of the IV and the tag length will depend on the cipher in use
           and will be defined in the RFC for the relevant ciphersuite.  In
           order to allow for "in place" decryption the plaintext output
           should be written to the same location in the output buffer that
           the ciphertext payload was read from, i.e. immediately after the
           explicit IV.

           When encrypting a record the first bytes of the input buffer should
           be empty to allow space for the explicit IV, as will the final
           bytes where the tag will be written.  The length of the input
           buffer will include the length of the explicit IV, the payload, and
           the tag bytes.  The cipher implementation should generate the
           explicit IV and write it to the beginning of the output buffer, do
           "in place" encryption of the payload and write that to the output
           buffer, and finally add the tag onto the end of the output buffer.

           Whether encrypting or decrypting the value written to *outl in the
           OSSL_FUNC_cipher_cipher call should be the length of the payload
           excluding the explicit IV length and the tag length.

       "tlsivinv" (OSSL_CIPHER_PARAM_AEAD_TLS1_SET_IV_INV) <octet string>
           Sets the invocation field used for decryption.  Can only be called
           after "tlsivfixed" is set.  This is only used for GCM mode.

       "tls1multi_enc" (OSSL_CIPHER_PARAM_TLS1_MULTIBLOCK_ENC) <octet string>
           Triggers a multiblock TLS1 encrypt operation for a TLS1 aware
           cipher that supports sending 4 or 8 records in one go.  The cipher
           performs both the MAC and encrypt stages and constructs the record
           headers itself.  "tls1multi_enc" supplies the output buffer for the
           encrypt operation, "tls1multi_encin" & "tls1multi_interleave" must
           also be set in order to supply values to the encrypt operation.

       "tls1multi_encin" (OSSL_CIPHER_PARAM_TLS1_MULTIBLOCK_ENC_IN) <octet
       string>
           Supplies the data to encrypt for a TLS1 multiblock cipher
           operation.

       "tls1multi_maxsndfrag"
       (OSSL_CIPHER_PARAM_TLS1_MULTIBLOCK_MAX_SEND_FRAGMENT) <unsigned
       integer>
           Sets the maximum send fragment size for a TLS1 multiblock cipher
           operation.  It must be set before using "tls1multi_maxbufsz".  The
           length of the "tls1multi_maxsndfrag" parameter should not exceed
           that of a size_t.

       "tls1multi_aad" (OSSL_CIPHER_PARAM_TLS1_MULTIBLOCK_AAD) <octet string>
           Sets the authenticated additional data used by a TLS1 multiblock
           cipher operation.  The supplied data consists of 13 bytes of record
           data containing: Bytes 0-7: The sequence number of the first record
           Byte 8: The record type Byte 9-10: The protocol version Byte 11-12:
           Input length (Always 0)

           "tls1multi_interleave" must also be set for this operation.

       "xts_standard" (OSSL_CIPHER_PARAM_XTS_STANDARD) <UTF8 string>
           Sets the XTS standard to use with SM4-XTS algorithm. XTS mode has
           two implementations, one is standardized in IEEE Std. 1619-2007 and
           has been widely used (e.g., XTS AES), the other is proposed
           recently (GB/T 17964-2021 implemented in May 2022) and is currently
           only used in SM4.

           The main difference between them is the multiplication by the
           primitive element X to calculate the tweak values. The IEEE Std
           1619-2007 noted that the multiplication "is a left shift of each
           byte by one bit with carry propagating from one byte to the next
           one", which means that in each byte, the leftmost bit is the most
           significant bit. But in GB/T 17964-2021, the rightmost bit is the
           most significant bit, thus the multiplication becomes a right shift
           of each byte by one bit with carry propagating from one byte to the
           next one.

           Valid values for the mode are:

           "GB"
               The GB/T 17964-2021 variant of SM4-XTS algorithm.

           "IEEE"
               The IEEE Std. 1619-2007 variant of SM4-XTS algorithm.

           The default value is "GB".


CONTROLS

       The Mappings from EVP_CIPHER_CTX_ctrl() identifiers to PARAMETERS are
       listed in the following section. See the "PARAMETERS" section for more
       details.

       EVP_CIPHER_CTX_ctrl() can be used to send the following standard
       controls:

       EVP_CTRL_AEAD_SET_IVLEN and EVP_CTRL_GET_IVLEN
           When used with a fetched EVP_CIPHER, EVP_CIPHER_CTX_set_params()
           and EVP_CIPHER_CTX_get_params() get called with an OSSL_PARAM(3)
           item with the key "ivlen" (OSSL_CIPHER_PARAM_IVLEN).

       EVP_CTRL_AEAD_SET_IV_FIXED
           When used with a fetched EVP_CIPHER, EVP_CIPHER_CTX_set_params()
           gets called with an OSSL_PARAM(3) item with the key "tlsivfixed"
           (OSSL_CIPHER_PARAM_AEAD_TLS1_IV_FIXED).

       EVP_CTRL_AEAD_SET_MAC_KEY
           When used with a fetched EVP_CIPHER, EVP_CIPHER_CTX_set_params()
           gets called with an OSSL_PARAM(3) item with the key "mackey"
           (OSSL_CIPHER_PARAM_AEAD_MAC_KEY).

       EVP_CTRL_AEAD_SET_TAG and EVP_CTRL_AEAD_GET_TAG
           When used with a fetched EVP_CIPHER, EVP_CIPHER_CTX_set_params()
           and EVP_CIPHER_CTX_get_params() get called with an OSSL_PARAM(3)
           item with the key "tag" (OSSL_CIPHER_PARAM_AEAD_TAG).

       EVP_CTRL_CCM_SET_L
           When used with a fetched EVP_CIPHER, EVP_CIPHER_CTX_set_params()
           gets called with an OSSL_PARAM(3) item with the key "ivlen"
           (OSSL_CIPHER_PARAM_IVLEN) with a value of (15 - L)

       EVP_CTRL_COPY
           There is no OSSL_PARAM mapping for this. Use EVP_CIPHER_CTX_copy()
           instead.

       EVP_CTRL_GCM_SET_IV_INV
           When used with a fetched EVP_CIPHER, EVP_CIPHER_CTX_set_params()
           gets called with an OSSL_PARAM(3) item with the key "tlsivinv"
           (OSSL_CIPHER_PARAM_AEAD_TLS1_SET_IV_INV).

       EVP_CTRL_RAND_KEY
           When used with a fetched EVP_CIPHER, EVP_CIPHER_CTX_set_params()
           gets called with an OSSL_PARAM(3) item with the key "randkey"
           (OSSL_CIPHER_PARAM_RANDOM_KEY).

       EVP_CTRL_SET_KEY_LENGTH
           When used with a fetched EVP_CIPHER, EVP_CIPHER_CTX_set_params()
           gets called with an OSSL_PARAM(3) item with the key "keylen"
           (OSSL_CIPHER_PARAM_KEYLEN).

       EVP_CTRL_SET_RC2_KEY_BITS and EVP_CTRL_GET_RC2_KEY_BITS
           When used with a fetched EVP_CIPHER, EVP_CIPHER_CTX_set_params()
           and EVP_CIPHER_CTX_get_params() get called with an OSSL_PARAM(3)
           item with the key "keybits" (OSSL_CIPHER_PARAM_RC2_KEYBITS).

       EVP_CTRL_SET_RC5_ROUNDS and EVP_CTRL_GET_RC5_ROUNDS
           When used with a fetched EVP_CIPHER, EVP_CIPHER_CTX_set_params()
           and EVP_CIPHER_CTX_get_params() get called with an OSSL_PARAM(3)
           item with the key "rounds" (OSSL_CIPHER_PARAM_ROUNDS).

       EVP_CTRL_SET_SPEED
           When used with a fetched EVP_CIPHER, EVP_CIPHER_CTX_set_params()
           gets called with an OSSL_PARAM(3) item with the key "speed"
           (OSSL_CIPHER_PARAM_SPEED).

       EVP_CTRL_GCM_IV_GEN
           When used with a fetched EVP_CIPHER, EVP_CIPHER_CTX_get_params()
           gets called with an OSSL_PARAM(3) item with the key "tlsivgen"
           (OSSL_CIPHER_PARAM_AEAD_TLS1_GET_IV_GEN).

       EVP_CTRL_AEAD_TLS1_AAD
           When used with a fetched EVP_CIPHER, EVP_CIPHER_CTX_set_params()
           get called with an OSSL_PARAM(3) item with the key "tlsaad"
           (OSSL_CIPHER_PARAM_AEAD_TLS1_AAD) followed by
           EVP_CIPHER_CTX_get_params() with a key of "tlsaadpad"
           (OSSL_CIPHER_PARAM_AEAD_TLS1_AAD_PAD).

       EVP_CTRL_TLS1_1_MULTIBLOCK_MAX_BUFSIZE
           When used with a fetched EVP_CIPHER, EVP_CIPHER_CTX_set_params()
           gets called with an OSSL_PARAM(3) item with the key
           OSSL_CIPHER_PARAM_TLS1_MULTIBLOCK_MAX_SEND_FRAGMENT followed by
           EVP_CIPHER_CTX_get_params() with a key of "tls1multi_maxbufsz"
           (OSSL_CIPHER_PARAM_TLS1_MULTIBLOCK_MAX_BUFSIZE).

       EVP_CTRL_TLS1_1_MULTIBLOCK_AAD
           When used with a fetched EVP_CIPHER, EVP_CIPHER_CTX_set_params()
           gets called with OSSL_PARAM(3) items with the keys "tls1multi_aad"
           (OSSL_CIPHER_PARAM_TLS1_MULTIBLOCK_AAD) and "tls1multi_interleave"
           (OSSL_CIPHER_PARAM_TLS1_MULTIBLOCK_INTERLEAVE) followed by
           EVP_CIPHER_CTX_get_params() with keys of "tls1multi_aadpacklen"
           (OSSL_CIPHER_PARAM_TLS1_MULTIBLOCK_AAD_PACKLEN) and
           "tls1multi_interleave"
           (OSSL_CIPHER_PARAM_TLS1_MULTIBLOCK_INTERLEAVE).

       EVP_CTRL_TLS1_1_MULTIBLOCK_ENCRYPT
           When used with a fetched EVP_CIPHER, EVP_CIPHER_CTX_set_params()
           gets called with OSSL_PARAM(3) items with the keys "tls1multi_enc"
           (OSSL_CIPHER_PARAM_TLS1_MULTIBLOCK_ENC), "tls1multi_encin"
           (OSSL_CIPHER_PARAM_TLS1_MULTIBLOCK_ENC_IN) and
           "tls1multi_interleave"
           (OSSL_CIPHER_PARAM_TLS1_MULTIBLOCK_INTERLEAVE), followed by
           EVP_CIPHER_CTX_get_params() with a key of "tls1multi_enclen"
           (OSSL_CIPHER_PARAM_TLS1_MULTIBLOCK_ENC_LEN).


FLAGS

       EVP_CIPHER_CTX_set_flags(), EVP_CIPHER_CTX_clear_flags() and
       EVP_CIPHER_CTX_test_flags().  can be used to manipulate and test these
       EVP_CIPHER_CTX flags:

       EVP_CIPH_NO_PADDING
           Used by EVP_CIPHER_CTX_set_padding().

           See also "Gettable and Settable EVP_CIPHER_CTX parameters"
           "padding"

       EVP_CIPH_FLAG_LENGTH_BITS
           See "Settable EVP_CIPHER_CTX parameters" "use-bits".

       EVP_CIPHER_CTX_FLAG_WRAP_ALLOW
           Used for Legacy purposes only. This flag needed to be set to
           indicate the cipher handled wrapping.

       EVP_CIPHER_flags() uses the following flags that have mappings to
       "Gettable EVP_CIPHER parameters":

       EVP_CIPH_FLAG_AEAD_CIPHER
           See "Gettable EVP_CIPHER parameters" "aead".

       EVP_CIPH_CUSTOM_IV
           See "Gettable EVP_CIPHER parameters" "custom-iv".

       EVP_CIPH_FLAG_CTS
           See "Gettable EVP_CIPHER parameters" "cts".

       EVP_CIPH_FLAG_TLS1_1_MULTIBLOCK;
           See "Gettable EVP_CIPHER parameters" "tls-multi".

       EVP_CIPH_RAND_KEY
           See "Gettable EVP_CIPHER parameters" "has-randkey".

       EVP_CIPHER_flags() uses the following flags for legacy purposes only:

       EVP_CIPH_VARIABLE_LENGTH
       EVP_CIPH_FLAG_CUSTOM_CIPHER
       EVP_CIPH_ALWAYS_CALL_INIT
       EVP_CIPH_CTRL_INIT
       EVP_CIPH_CUSTOM_KEY_LENGTH
       EVP_CIPH_CUSTOM_COPY
       EVP_CIPH_FLAG_DEFAULT_ASN1
           See EVP_CIPHER_meth_set_flags(3) for further information related to
           the above flags.


RETURN VALUES

       EVP_CIPHER_fetch() returns a pointer to a EVP_CIPHER for success and
       NULL for failure.

       EVP_CIPHER_up_ref() returns 1 for success or 0 otherwise.

       EVP_CIPHER_CTX_new() returns a pointer to a newly created
       EVP_CIPHER_CTX for success and NULL for failure.

       EVP_CIPHER_CTX_dup() returns a new EVP_MD_CTX if successful or NULL on
       failure.

       EVP_CIPHER_CTX_copy() returns 1 if successful or 0 for failure.

       EVP_EncryptInit_ex2(), EVP_EncryptUpdate() and EVP_EncryptFinal_ex()
       return 1 for success and 0 for failure.

       EVP_DecryptInit_ex2() and EVP_DecryptUpdate() return 1 for success and
       0 for failure.  EVP_DecryptFinal_ex() returns 0 if the decrypt failed
       or 1 for success.

       EVP_CipherInit_ex2() and EVP_CipherUpdate() return 1 for success and 0
       for failure.  EVP_CipherFinal_ex() returns 0 for a decryption failure
       or 1 for success.

       EVP_Cipher() returns 1 on success or 0 on failure, if the flag
       EVP_CIPH_FLAG_CUSTOM_CIPHER is not set for the cipher.  EVP_Cipher()
       returns the number of bytes written to out for encryption / decryption,
       or the number of bytes authenticated in a call specifying AAD for an
       AEAD cipher, if the flag EVP_CIPH_FLAG_CUSTOM_CIPHER is set for the
       cipher.

       EVP_CIPHER_CTX_reset() returns 1 for success and 0 for failure.

       EVP_get_cipherbyname(), EVP_get_cipherbynid() and EVP_get_cipherbyobj()
       return an EVP_CIPHER structure or NULL on error.

       EVP_CIPHER_get_nid() and EVP_CIPHER_CTX_get_nid() return a NID.

       EVP_CIPHER_get_block_size() and EVP_CIPHER_CTX_get_block_size() return
       the block size.

       EVP_CIPHER_get_key_length() and EVP_CIPHER_CTX_get_key_length() return
       the key length.

       EVP_CIPHER_CTX_set_padding() always returns 1.

       EVP_CIPHER_get_iv_length() and EVP_CIPHER_CTX_get_iv_length() return
       the IV length, zero if the cipher does not use an IV and a negative
       value on error.

       EVP_CIPHER_CTX_get_tag_length() return the tag length or zero if the
       cipher does not use a tag.

       EVP_CIPHER_get_type() and EVP_CIPHER_CTX_get_type() return the NID of
       the cipher's OBJECT IDENTIFIER or NID_undef if it has no defined OBJECT
       IDENTIFIER.

       EVP_CIPHER_CTX_cipher() returns an EVP_CIPHER structure.

       EVP_CIPHER_CTX_get_num() returns a nonnegative num value or
       EVP_CTRL_RET_UNSUPPORTED if the implementation does not support the
       call or on any other error.

       EVP_CIPHER_CTX_set_num() returns 1 on success and 0 if the
       implementation does not support the call or on any other error.

       EVP_CIPHER_CTX_is_encrypting() returns 1 if the ctx is set up for
       encryption 0 otherwise.

       EVP_CIPHER_param_to_asn1() and EVP_CIPHER_asn1_to_param() return
       greater than zero for success and zero or a negative number on failure.

       EVP_CIPHER_CTX_rand_key() returns 1 for success and zero or a negative
       number for failure.

       EVP_CIPHER_names_do_all() returns 1 if the callback was called for all
       names.  A return value of 0 means that the callback was not called for
       any names.


CIPHER LISTING

       All algorithms have a fixed key length unless otherwise stated.

       Refer to "SEE ALSO" for the full list of ciphers available through the
       EVP interface.

       EVP_enc_null()
           Null cipher: does nothing.


AEAD INTERFACE

       The EVP interface for Authenticated Encryption with Associated Data
       (AEAD) modes are subtly altered and several additional ctrl operations
       are supported depending on the mode specified.

       To specify additional authenticated data (AAD), a call to
       EVP_CipherUpdate(), EVP_EncryptUpdate() or EVP_DecryptUpdate() should
       be made with the output parameter out set to NULL. In this case, on
       success, the parameter outl is set to the number of bytes
       authenticated.

       When decrypting, the return value of EVP_DecryptFinal() or
       EVP_CipherFinal() indicates whether the operation was successful. If it
       does not indicate success, the authentication operation has failed and
       any output data MUST NOT be used as it is corrupted.

   GCM and OCB Modes
       The following ctrls are supported in GCM and OCB modes.

       EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_IVLEN, ivlen, NULL)
           Sets the IV length. This call can only be made before specifying an
           IV. If not called a default IV length is used.

           For GCM AES and OCB AES the default is 12 (i.e. 96 bits). For OCB
           mode the maximum is 15.

       EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_GET_TAG, taglen, tag)
           Writes "taglen" bytes of the tag value to the buffer indicated by
           "tag".  This call can only be made when encrypting data and after
           all data has been processed (e.g. after an EVP_EncryptFinal()
           call).

           For OCB, "taglen" must either be 16 or the value previously set via
           EVP_CTRL_AEAD_SET_TAG.

       EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_TAG, taglen, tag)
           When decrypting, this call sets the expected tag to "taglen" bytes
           from "tag".  "taglen" must be between 1 and 16 inclusive.  The tag
           must be set prior to any call to EVP_DecryptFinal() or
           EVP_DecryptFinal_ex().

           For GCM, this call is only valid when decrypting data.

           For OCB, this call is valid when decrypting data to set the
           expected tag, and when encrypting to set the desired tag length.

           In OCB mode, calling this when encrypting with "tag" set to "NULL"
           sets the tag length. The tag length can only be set before
           specifying an IV. If this is not called prior to setting the IV
           during encryption, then a default tag length is used.

           For OCB AES, the default tag length is 16 (i.e. 128 bits).  It is
           also the maximum tag length for OCB.

   CCM Mode
       The EVP interface for CCM mode is similar to that of the GCM mode but
       with a few additional requirements and different ctrl values.

       For CCM mode, the total plaintext or ciphertext length MUST be passed
       to EVP_CipherUpdate(), EVP_EncryptUpdate() or EVP_DecryptUpdate() with
       the output and input parameters (in and out) set to NULL and the length
       passed in the inl parameter.

       The following ctrls are supported in CCM mode.

       EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_TAG, taglen, tag)
           This call is made to set the expected CCM tag value when decrypting
           or the length of the tag (with the "tag" parameter set to NULL)
           when encrypting.  The tag length is often referred to as M. If not
           set a default value is used (12 for AES). When decrypting, the tag
           needs to be set before passing in data to be decrypted, but as in
           GCM and OCB mode, it can be set after passing additional
           authenticated data (see "AEAD INTERFACE").

       EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_CCM_SET_L, ivlen, NULL)
           Sets the CCM L value. If not set a default is used (8 for AES).

       EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_IVLEN, ivlen, NULL)
           Sets the CCM nonce (IV) length. This call can only be made before
           specifying a nonce value. The nonce length is given by 15 - L so it
           is 7 by default for AES.

   SIV Mode
       Both the AES-SIV and AES-GCM-SIV ciphers fall under this mode.

       For SIV mode ciphers the behaviour of the EVP interface is subtly
       altered and several additional ctrl operations are supported.

       To specify any additional authenticated data (AAD) and/or a Nonce, a
       call to EVP_CipherUpdate(), EVP_EncryptUpdate() or EVP_DecryptUpdate()
       should be made with the output parameter out set to NULL.

       RFC5297 states that the Nonce is the last piece of AAD before the
       actual encrypt/decrypt takes place. The API does not differentiate the
       Nonce from other AAD.

       When decrypting the return value of EVP_DecryptFinal() or
       EVP_CipherFinal() indicates if the operation was successful. If it does
       not indicate success the authentication operation has failed and any
       output data MUST NOT be used as it is corrupted.

       The API does not store the the SIV (Synthetic Initialization Vector) in
       the cipher text. Instead, it is stored as the tag within the
       EVP_CIPHER_CTX. The SIV must be retrieved from the context after
       encryption, and set into the context before decryption.

       This differs from RFC5297 in that the cipher output from encryption,
       and the cipher input to decryption, does not contain the SIV. This also
       means that the plain text and cipher text lengths are identical.

       The following ctrls are supported in SIV mode, and are used to get and
       set the Synthetic Initialization Vector:

       EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_GET_TAG, taglen, tag);
           Writes taglen bytes of the tag value (the Synthetic Initialization
           Vector) to the buffer indicated by tag. This call can only be made
           when encrypting data and after all data has been processed (e.g.
           after an EVP_EncryptFinal() call). For SIV mode the taglen must be
           16.

       EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_TAG, taglen, tag);
           Sets the expected tag (the Synthetic Initialization Vector) to
           taglen bytes from tag. This call is only legal when decrypting data
           and must be made before any data is processed (e.g. before any
           EVP_DecryptUpdate() calls). For SIV mode the taglen must be 16.

       SIV mode makes two passes over the input data, thus, only one call to
       EVP_CipherUpdate(), EVP_EncryptUpdate() or EVP_DecryptUpdate() should
       be made with out set to a non-NULL value. A call to EVP_DecryptFinal()
       or EVP_CipherFinal() is not required, but will indicate if the update
       operation succeeded.

   ChaCha20-Poly1305
       The following ctrls are supported for the ChaCha20-Poly1305 AEAD
       algorithm.

       EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_IVLEN, ivlen, NULL)
           Sets the nonce length. This call is now redundant since the only
           valid value is the default length of 12 (i.e. 96 bits).  Prior to
           OpenSSL 3.0 a nonce of less than 12 bytes could be used to
           automatically pad the iv with leading 0 bytes to make it 12 bytes
           in length.

       EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_GET_TAG, taglen, tag)
           Writes "taglen" bytes of the tag value to the buffer indicated by
           "tag".  This call can only be made when encrypting data and after
           all data has been processed (e.g. after an EVP_EncryptFinal()
           call).

           "taglen" specified here must be 16 (POLY1305_BLOCK_SIZE, i.e.
           128-bits) or less.

       EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_TAG, taglen, tag)
           Sets the expected tag to "taglen" bytes from "tag".  The tag length
           can only be set before specifying an IV. "taglen" must be between 1
           and 16 (POLY1305_BLOCK_SIZE) inclusive.  This call is only valid
           when decrypting data.


NOTES

       Where possible the EVP interface to symmetric ciphers should be used in
       preference to the low-level interfaces. This is because the code then
       becomes transparent to the cipher used and much more flexible.
       Additionally, the EVP interface will ensure the use of platform
       specific cryptographic acceleration such as AES-NI (the low-level
       interfaces do not provide the guarantee).

       PKCS padding works by adding n padding bytes of value n to make the
       total length of the encrypted data a multiple of the block size.
       Padding is always added so if the data is already a multiple of the
       block size n will equal the block size. For example if the block size
       is 8 and 11 bytes are to be encrypted then 5 padding bytes of value 5
       will be added.

       When decrypting the final block is checked to see if it has the correct
       form.

       Although the decryption operation can produce an error if padding is
       enabled, it is not a strong test that the input data or key is correct.
       A random block has better than 1 in 256 chance of being of the correct
       format and problems with the input data earlier on will not produce a
       final decrypt error.

       If padding is disabled then the decryption operation will always
       succeed if the total amount of data decrypted is a multiple of the
       block size.

       The functions EVP_EncryptInit(3), EVP_EncryptInit_ex(),
       EVP_EncryptFinal(), EVP_DecryptInit(), EVP_DecryptInit_ex(),
       EVP_CipherInit(), EVP_CipherInit_ex() and EVP_CipherFinal() are
       obsolete but are retained for compatibility with existing code. New
       code should use EVP_EncryptInit_ex2(), EVP_EncryptFinal_ex(),
       EVP_DecryptInit_ex2(), EVP_DecryptFinal_ex(), EVP_CipherInit_ex2() and
       EVP_CipherFinal_ex() because they can reuse an existing context without
       allocating and freeing it up on each call.

       There are some differences between functions EVP_CipherInit() and
       EVP_CipherInit_ex(), significant in some circumstances.
       EVP_CipherInit() fills the passed context object with zeros.  As a
       consequence, EVP_CipherInit() does not allow step-by-step
       initialization of the ctx when the key and iv are passed in separate
       calls. It also means that the flags set for the CTX are removed, and it
       is especially important for the EVP_CIPHER_CTX_FLAG_WRAP_ALLOW flag
       treated specially in EVP_CipherInit_ex().

       Ignoring failure returns of the EVP_CIPHER_CTX initialization functions
       can lead to subsequent undefined behavior when calling the functions
       that update or finalize the context. The only valid calls on the
       EVP_CIPHER_CTX when initialization fails are calls that attempt another
       initialization of the context or release the context.

       EVP_get_cipherbynid(), and EVP_get_cipherbyobj() are implemented as
       macros.


BUGS

       EVP_MAX_KEY_LENGTH and EVP_MAX_IV_LENGTH only refer to the internal
       ciphers with default key lengths. If custom ciphers exceed these values
       the results are unpredictable. This is because it has become standard
       practice to define a generic key as a fixed unsigned char array
       containing EVP_MAX_KEY_LENGTH bytes.

       The ASN1 code is incomplete (and sometimes inaccurate) it has only been
       tested for certain common S/MIME ciphers (RC2, DES, triple DES) in CBC
       mode.


EXAMPLES

       Encrypt a string using IDEA:

        int do_crypt(char *outfile)
        {
            unsigned char outbuf[1024];
            int outlen, tmplen;
            /*
             * Bogus key and IV: we'd normally set these from
             * another source.
             */
            unsigned char key[] = {0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15};
            unsigned char iv[] = {1,2,3,4,5,6,7,8};
            char intext[] = "Some Crypto Text";
            EVP_CIPHER_CTX *ctx;
            FILE *out;

            ctx = EVP_CIPHER_CTX_new();
            if (!EVP_EncryptInit_ex2(ctx, EVP_idea_cbc(), key, iv, NULL)) {
                /* Error */
                EVP_CIPHER_CTX_free(ctx);
                return 0;
            }

            if (!EVP_EncryptUpdate(ctx, outbuf, &outlen, intext, strlen(intext))) {
                /* Error */
                EVP_CIPHER_CTX_free(ctx);
                return 0;
            }
            /*
             * Buffer passed to EVP_EncryptFinal() must be after data just
             * encrypted to avoid overwriting it.
             */
            if (!EVP_EncryptFinal_ex(ctx, outbuf + outlen, &tmplen)) {
                /* Error */
                EVP_CIPHER_CTX_free(ctx);
                return 0;
            }
            outlen += tmplen;
            EVP_CIPHER_CTX_free(ctx);
            /*
             * Need binary mode for fopen because encrypted data is
             * binary data. Also cannot use strlen() on it because
             * it won't be NUL terminated and may contain embedded
             * NULs.
             */
            out = fopen(outfile, "wb");
            if (out == NULL) {
                /* Error */
                return 0;
            }
            fwrite(outbuf, 1, outlen, out);
            fclose(out);
            return 1;
        }

       The ciphertext from the above example can be decrypted using the
       openssl utility with the command line (shown on two lines for clarity):

        openssl idea -d \
            -K 000102030405060708090A0B0C0D0E0F -iv 0102030405060708 <filename

       General encryption and decryption function example using FILE I/O and
       AES128 with a 128-bit key:

        int do_crypt(FILE *in, FILE *out, int do_encrypt)
        {
            /* Allow enough space in output buffer for additional block */
            unsigned char inbuf[1024], outbuf[1024 + EVP_MAX_BLOCK_LENGTH];
            int inlen, outlen;
            EVP_CIPHER_CTX *ctx;
            /*
             * Bogus key and IV: we'd normally set these from
             * another source.
             */
            unsigned char key[] = "0123456789abcdeF";
            unsigned char iv[] = "1234567887654321";

            /* Don't set key or IV right away; we want to check lengths */
            ctx = EVP_CIPHER_CTX_new();
            if (!EVP_CipherInit_ex2(ctx, EVP_aes_128_cbc(), NULL, NULL,
                                    do_encrypt, NULL)) {
                /* Error */
                EVP_CIPHER_CTX_free(ctx);
                return 0;
            }
            OPENSSL_assert(EVP_CIPHER_CTX_get_key_length(ctx) == 16);
            OPENSSL_assert(EVP_CIPHER_CTX_get_iv_length(ctx) == 16);

            /* Now we can set key and IV */
            if (!EVP_CipherInit_ex2(ctx, NULL, key, iv, do_encrypt, NULL)) {
                /* Error */
                EVP_CIPHER_CTX_free(ctx);
                return 0;
            }

            for (;;) {
                inlen = fread(inbuf, 1, 1024, in);
                if (inlen <= 0)
                    break;
                if (!EVP_CipherUpdate(ctx, outbuf, &outlen, inbuf, inlen)) {
                    /* Error */
                    EVP_CIPHER_CTX_free(ctx);
                    return 0;
                }
                fwrite(outbuf, 1, outlen, out);
            }
            if (!EVP_CipherFinal_ex(ctx, outbuf, &outlen)) {
                /* Error */
                EVP_CIPHER_CTX_free(ctx);
                return 0;
            }
            fwrite(outbuf, 1, outlen, out);

            EVP_CIPHER_CTX_free(ctx);
            return 1;
        }

       Encryption using AES-CBC with a 256-bit key with "CS1" ciphertext
       stealing.

        int encrypt(const unsigned char *key, const unsigned char *iv,
                    const unsigned char *msg, size_t msg_len, unsigned char *out)
        {
           /*
            * This assumes that key size is 32 bytes and the iv is 16 bytes.
            * For ciphertext stealing mode the length of the ciphertext "out" will be
            * the same size as the plaintext size "msg_len".
            * The "msg_len" can be any size >= 16.
            */
            int ret = 0, encrypt = 1, outlen, len;
            EVP_CIPHER_CTX *ctx = NULL;
            EVP_CIPHER *cipher = NULL;
            OSSL_PARAM params[2];

            ctx = EVP_CIPHER_CTX_new();
            cipher = EVP_CIPHER_fetch(NULL, "AES-256-CBC-CTS", NULL);
            if (ctx == NULL || cipher == NULL)
                goto err;

            /*
             * The default is "CS1" so this is not really needed,
             * but would be needed to set either "CS2" or "CS3".
             */
            params[0] = OSSL_PARAM_construct_utf8_string(OSSL_CIPHER_PARAM_CTS_MODE,
                                                         "CS1", 0);
            params[1] = OSSL_PARAM_construct_end();

            if (!EVP_CipherInit_ex2(ctx, cipher, key, iv, encrypt, params))
                goto err;

            /* NOTE: CTS mode does not support multiple calls to EVP_CipherUpdate() */
            if (!EVP_CipherUpdate(ctx, out, &outlen, msg, msg_len))
                goto err;
             if (!EVP_CipherFinal_ex(ctx, out + outlen, &len))
                goto err;
            ret = 1;
        err:
            EVP_CIPHER_free(cipher);
            EVP_CIPHER_CTX_free(ctx);
            return ret;
        }


SEE ALSO

       evp(7), property(7), "ALGORITHM FETCHING" in crypto(7),
       provider-cipher(7), life_cycle-cipher(7)

       Supported ciphers are listed in:

       EVP_aes_128_gcm(3), EVP_aria_128_gcm(3), EVP_bf_cbc(3),
       EVP_camellia_128_ecb(3), EVP_cast5_cbc(3), EVP_chacha20(3),
       EVP_des_cbc(3), EVP_desx_cbc(3), EVP_idea_cbc(3), EVP_rc2_cbc(3),
       EVP_rc4(3), EVP_rc5_32_12_16_cbc(3), EVP_seed_cbc(3), EVP_sm4_cbc(3),


HISTORY

       Support for OCB mode was added in OpenSSL 1.1.0.

       EVP_CIPHER_CTX was made opaque in OpenSSL 1.1.0.  As a result,
       EVP_CIPHER_CTX_reset() appeared and EVP_CIPHER_CTX_cleanup()
       disappeared.  EVP_CIPHER_CTX_init() remains as an alias for
       EVP_CIPHER_CTX_reset().

       The EVP_CIPHER_CTX_cipher() function was deprecated in OpenSSL 3.0; use
       EVP_CIPHER_CTX_get0_cipher() instead.

       The EVP_EncryptInit_ex2(), EVP_DecryptInit_ex2(), EVP_CipherInit_ex2(),
       EVP_CIPHER_fetch(), EVP_CIPHER_free(), EVP_CIPHER_up_ref(),
       EVP_CIPHER_CTX_get0_cipher(), EVP_CIPHER_CTX_get1_cipher(),
       EVP_CIPHER_get_params(), EVP_CIPHER_CTX_set_params(),
       EVP_CIPHER_CTX_get_params(), EVP_CIPHER_gettable_params(),
       EVP_CIPHER_settable_ctx_params(), EVP_CIPHER_gettable_ctx_params(),
       EVP_CIPHER_CTX_settable_params() and EVP_CIPHER_CTX_gettable_params()
       functions were added in 3.0.

       The EVP_CIPHER_nid(), EVP_CIPHER_name(), EVP_CIPHER_block_size(),
       EVP_CIPHER_key_length(), EVP_CIPHER_iv_length(), EVP_CIPHER_flags(),
       EVP_CIPHER_mode(), EVP_CIPHER_type(), EVP_CIPHER_CTX_nid(),
       EVP_CIPHER_CTX_block_size(), EVP_CIPHER_CTX_key_length(),
       EVP_CIPHER_CTX_iv_length(), EVP_CIPHER_CTX_tag_length(),
       EVP_CIPHER_CTX_num(), EVP_CIPHER_CTX_type(), and EVP_CIPHER_CTX_mode()
       functions were renamed to include "get" or "get0" in their names in
       OpenSSL 3.0, respectively. The old names are kept as non-deprecated
       alias macros.

       The EVP_CIPHER_CTX_encrypting() function was renamed to
       EVP_CIPHER_CTX_is_encrypting() in OpenSSL 3.0. The old name is kept as
       non-deprecated alias macro.

       The EVP_CIPHER_CTX_flags() macro was deprecated in OpenSSL 1.1.0.

       EVP_CIPHER_CTX_dup() was added in OpenSSL 3.2.


COPYRIGHT

       Copyright 2000-2023 The OpenSSL Project Authors. All Rights Reserved.

       Licensed under the Apache License 2.0 (the "License").  You may not use
       this file except in compliance with the License.  You can obtain a copy
       in the file LICENSE in the source distribution or at
       <https://www.openssl.org/source/license.html>.

3.2.0                             2023-11-23            EVP_ENCRYPTINIT(3ossl)

openssl 3.2.0 - Generated Thu Nov 30 10:27:39 CST 2023
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