Crypt::PRNG(3) User Contributed Perl Documentation Crypt::PRNG(3)
NAME
Crypt::PRNG - Cryptographically secure random number generator
SYNOPSIS
### Functional interface:
use Crypt::PRNG qw(random_bytes random_bytes_hex random_bytes_b64 random_bytes_b64u
random_string random_string_from rand irand);
my $octets = random_bytes(45);
my $hex_string = random_bytes_hex(45);
my $base64_string = random_bytes_b64(45);
my $base64url_string = random_bytes_b64u(45);
my $alphanumeric_string = random_string(30);
my $string = random_string_from('ACGT', 64);
my $floating_point_number_0_to_1 = rand;
my $floating_point_number_0_to_88 = rand(88);
my $unsigned_32bit_int = irand;
### OO interface:
use Crypt::PRNG;
my $prng = Crypt::PRNG->new; # defaults to ChaCha20
my $rc4_prng = Crypt::PRNG->new("RC4");
my $seeded_prng = Crypt::PRNG->new("RC4", "some data used for seeding PRNG");
my $octets = $prng->bytes(45);
my $hex_string = $prng->bytes_hex(45);
my $base64_string = $prng->bytes_b64(45);
my $base64url_string = $prng->bytes_b64u(45);
my $alphanumeric_string = $prng->string(30);
my $string = $prng->string_from('ACGT', 64);
my $floating_point_number_0_to_1 = $prng->double;
my $floating_point_number_0_to_88 = $prng->double(88);
my $unsigned_32bit_int = $prng->int32;
DESCRIPTION
Provides an interface to several pseudo-random number generators
(thread-safe and fork-safe). The default algorithm is ChaCha20.
EXPORT
Nothing is exported by default.
You can export selected functions:
use Crypt::PRNG qw(random_bytes random_string);
Or all of them at once:
use Crypt::PRNG ':all';
FUNCTIONS
For all "random_bytes*" functions and the corresponding "bytes*"
methods, $length must not be greater than 1000000000.
random_bytes
my $octets = random_bytes($length);
# $length .. [integer] number of random bytes to generate
Returns $length random octets as a binary string.
random_bytes_hex
my $hex_string = random_bytes_hex($length);
# $length .. [integer] number of random bytes (output string will be 2x longer)
Returns $length random octets encoded as a lowercase hexadecimal
string.
random_bytes_b64
my $base64_string = random_bytes_b64($length);
# $length .. [integer] number of random bytes to encode
Returns $length random octets encoded as a Base64 string.
random_bytes_b64u
my $base64url_string = random_bytes_b64u($length);
# $length .. [integer] number of random bytes to encode
Returns $length random octets encoded as a Base64 URL-safe string (RFC
4648 section 5).
random_string_from
my $string = random_string_from($range, $length);
# $range .. [string] alphabet of allowed characters
# $length .. [integer] optional, number of characters (DEFAULT: 20)
#e.g.
my $dna_string = random_string_from("ABCD", 10);
Returns a random string of $length characters chosen from $range. The
alphabet must contain between 1 and 65536 characters; longer alphabets
return "undef".
random_string
my $alphanumeric_string = random_string($length);
# $length .. [integer] optional, number of characters (DEFAULT: 20)
#or
my $default_alphanumeric_string = random_string; # default length = 20
Like "random_string_from", but $range is fixed to
'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789'.
rand
my $n = rand;
#or
my $limited_n = rand($limit);
# $limit .. [number] optional, upper bound (exclusive)
Returns a random floating-point number in the range "[0,1)" if called
without an argument, or "[0,$limit)" if $limit is given. If $limit is
0, this behaves as if no limit was given and returns a value in
"[0,1)", matching Perl's built-in "rand".
irand
my $i = irand;
Returns a random unsigned 32-bit integer in the range "0 ..
0xFFFFFFFF".
METHODS
Unless noted otherwise, assume $prng is an existing PRNG object created
via "new", for example:
my $prng = Crypt::PRNG->new;
new
my $prng = Crypt::PRNG->new; # defaults to ChaCha20
#or
my $prng = Crypt::PRNG->new($alg);
#or
my $prng = Crypt::PRNG->new($alg, $seed);
# $alg ... [string] algorithm name: 'ChaCha20' (DEFAULT), 'Fortuna', 'RC4' (legacy; compatibility only), 'Sober128' or 'Yarrow'
# $seed ... [binary string] optional, initial entropy for seeding the PRNG
If $seed is not given, the PRNG is automatically seeded with 40 bytes
obtained via libtomcrypt's rng_get_bytes() platform RNG logic.
If $seed is specified it must be non-empty for all algorithms. RC4 is
provided for legacy compatibility only, is not recommended for new
designs, and requires a seed of at least 5 bytes.
add_entropy
my $prng = Crypt::PRNG->new;
$prng->add_entropy($random_data);
#or
$prng->add_entropy();
If called without parameter it uses 40 bytes obtained via libtomcrypt's
rng_get_bytes() platform RNG logic.
Note: You probably do not need this function. The module seeds itself
on initialization and reseeds after fork and thread creation.
bytes
my $octets = $prng->bytes($length);
See random_bytes
bytes_hex
my $hex_string = $prng->bytes_hex($length);
See random_bytes_hex
bytes_b64
my $base64_string = $prng->bytes_b64($length);
See random_bytes_b64
bytes_b64u
my $base64url_string = $prng->bytes_b64u($length);
See random_bytes_b64u
string
my $alphanumeric_string = $prng->string($length);
#or
my $default_alphanumeric_string = $prng->string; # default length = 20
See random_string
string_from
my $string = $prng->string_from($range, $length); # default length = 20
See random_string_from
double
my $n = $prng->double;
#or
my $limited_n = $prng->double($limit);
See rand
int32
my $i = $prng->int32;
See irand
SEE ALSO
Crypt::PRNG::ChaCha20(3), Crypt::PRNG::Fortuna(3), Crypt::PRNG::RC4(3),
Crypt::PRNG::Sober128(3), Crypt::PRNG::Yarrow(3)
For generating random UUIDs see "random_v4uuid" in Crypt::Misc(3) and
"random_v7uuid" in Crypt::Misc(3).
perl v5.34.3 2026-05-11 Crypt::PRNG(3)
cryptx 0.89.0 - Generated Tue May 12 09:24:34 CDT 2026