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OSSL_ALGORITHM(3ossl)                OpenSSL               OSSL_ALGORITHM(3ossl)


       OSSL_ALGORITHM - OpenSSL Core type to define a fetchable algorithm


        #include <openssl/core.h>

        typedef struct ossl_algorithm_st OSSL_ALGORITHM;
        struct ossl_algorithm_st {
            const char *algorithm_names;     /* key */
            const char *property_definition; /* key */
            const OSSL_DISPATCH *implementation;
            const char *algorithm_description;


       The OSSL_ALGORITHM type is a public structure that describes an algorithm
       that a provider(7) provides.  Arrays of this type are returned by
       providers on demand from the OpenSSL libraries to describe what
       algorithms the providers provide implementations of, and with what

       Arrays of this type must be terminated with a tuple where algorithm_names
       is NULL.

       This type of array is typically returned by the provider's operation
       querying function, further described in "Provider Functions" in

           This string is a colon separated set of names / identities, and is
           used by the appropriate fetching functionality (such as
           EVP_CIPHER_fetch(3), EVP_MD_fetch(3), etc) to find the desired

           Multiple names / identities allow a specific algorithm implementation
           to be fetched multiple ways.  For example, the RSA algorithm has the
           following known identities:

           o   "RSA"

           o   "rsaEncryption"

               This is the name of the algorithm's OBJECT IDENTIFIER (OID), as
               given by the PKCS#1 RFC's ASN.1 module <https://www.rfc-

           o   1.2.840.113549.1.1.1

               This is the OID itself for "rsaEncryption", in canonical decimal
               text form.

           The resulting algorithm_names string would look like this:


           The OpenSSL libraries use the first of the algorithm names as the
           main or canonical name, on a per algorithm implementation basis.

           See the notes "On the subject of algorithm names" below for a more in
           depth discussion on algorithm_names and how that may interact with
           applications and libraries, including OpenSSL's.

           This string defines a set of properties associated with a particular
           algorithm implementation, and is used by the appropriate fetching
           functionality (such as EVP_CIPHER_fetch(3), EVP_MD_fetch(3), etc) for
           a finer grained lookup of an algorithm implementation, which is
           useful in case multiple implementations of the same algorithm are

           See property(7) for a further description of the contents of this

           Pointer to an OSSL_DISPATCH(3) array, containing pointers to the
           functions of a particular algorithm implementation.

           A string with a short human-readable description of the algorithm.


   On the subject of algorithm names
       Providers may find the need to register ASN.1 OIDs for algorithms using
       OBJ_create(3) (via the core_obj_create upcall described in
       provider-base(7), because some application or library -- possibly still
       the OpenSSL libraries, even -- use NIDs to look up algorithms.

       In that scenario, you must make sure that the corresponding
       OSSL_ALGORITHM's algorithm_names includes both the short and the long

       Most of the time, registering ASN.1 OIDs like this shouldn't be
       necessary, and applications and libraries are encouraged to use
       OBJ_obj2txt(3) to get a text representation of the OID, which may be a
       long or short name for OIDs that are registered, or the OID itself in
       canonical decimal text form if not (or if OBJ_obj2txt(3) is called with
       no_name = 1).

       It's recommended to make sure that the corresponding OSSL_ALGORITHM's
       algorithm_names include known names as well as the OID itself in
       canonical decimal text form.  That should cover all scenarios.


       crypto(7), provider-base(7), openssl-core.h(7),
       openssl-core_dispatch.h(7), OSSL_DISPATCH(3)


       OSSL_ALGORITHM was added in OpenSSL 3.0


       Copyright 2022 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

3.0.8                              2023-02-07              OSSL_ALGORITHM(3ossl)

openssl 3.0.8 - Generated Fri Feb 10 15:12:50 CST 2023
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