# phpman > man > Crypt::PRNG(3pm)

## NAME
    [Crypt::PRNG](https://www.chedong.com/phpMan.php/perldoc/Crypt%3A%3APRNG/markdown) - Cryptographically secure random number generator

## SYNOPSIS
       ### Functional interface:
       use [Crypt::PRNG](https://www.chedong.com/phpMan.php/perldoc/Crypt%3A%3APRNG/markdown) qw(random_bytes random_bytes_hex random_bytes_b64 random_bytes_b64u
                          random_string random_string_from rand irand);

       $octets = [random_bytes(45)](https://www.chedong.com/phpMan.php/man/randombytes/45/markdown);
       $hex_string = [random_bytes_hex(45)](https://www.chedong.com/phpMan.php/man/randombyteshex/45/markdown);
       $base64_string = [random_bytes_b64(45)](https://www.chedong.com/phpMan.php/man/randombytesb64/45/markdown);
       $base64url_string = [random_bytes_b64u(45)](https://www.chedong.com/phpMan.php/man/randombytesb64u/45/markdown);
       $alphanumeric_string = [random_string(30)](https://www.chedong.com/phpMan.php/man/randomstring/30/markdown);
       $string = random_string_from('ACGT', 64);
       $floating_point_number_0_to_1 = rand;
       $floating_point_number_0_to_88 = [rand(88)](https://www.chedong.com/phpMan.php/man/rand/88/markdown);
       $unsigned_32bit_int = irand;

       ### OO interface:
       use [Crypt::PRNG](https://www.chedong.com/phpMan.php/perldoc/Crypt%3A%3APRNG/markdown);

       $prng = [Crypt::PRNG](https://www.chedong.com/phpMan.php/perldoc/Crypt%3A%3APRNG/markdown)->new;
       #or
       $prng = [Crypt::PRNG](https://www.chedong.com/phpMan.php/perldoc/Crypt%3A%3APRNG/markdown)->new("RC4");
       #or
       $prng = [Crypt::PRNG](https://www.chedong.com/phpMan.php/perldoc/Crypt%3A%3APRNG/markdown)->new("RC4", "some data used for seeding PRNG");

       $octets = $prng->[bytes(45)](https://www.chedong.com/phpMan.php/man/bytes/45/markdown);
       $hex_string = $prng->[bytes_hex(45)](https://www.chedong.com/phpMan.php/man/byteshex/45/markdown);
       $base64_string = $prng->[bytes_b64(45)](https://www.chedong.com/phpMan.php/man/bytesb64/45/markdown);
       $base64url_string = $prng->[bytes_b64u(45)](https://www.chedong.com/phpMan.php/man/bytesb64u/45/markdown);
       $alphanumeric_string = $prng->[string(30)](https://www.chedong.com/phpMan.php/man/string/30/markdown);
       $string = $prng->string_from('ACGT', 64);
       $floating_point_number_0_to_1 = $prng->double;
       $floating_point_number_0_to_88 = $prng->[double(88)](https://www.chedong.com/phpMan.php/man/double/88/markdown);
       $unsigned_32bit_int = $prng->int32;

## DESCRIPTION
    Provides an interface to the ChaCha20 based pseudo random number generator (thread-safe and
    fork-safe).

## FUNCTIONS
  random_bytes
       $octets = random_bytes($length);

    Returns $length random octects.

  random_bytes_hex
       $hex_string = random_bytes_hex($length);

    Returns $length random octects encoded as hexadecimal string.

  random_bytes_b64
       $base64_string = random_bytes_b64($length);

    Returns $length random octects Base64 encoded.

  random_bytes_b64u
       $base64url_string = random_bytes_b64u($length);

    Returns $length random octects Base64 URL Safe (RFC 4648 section 5) encoded.

  random_string_from
       $string = random_string_from($range, $length);
       #e.g.
       $string = random_string_from("ABCD", 10);

    Returns a random string made of $length chars randomly chosen from $range string.

  random_string
       $alphanumeric_string = random_string($length);
       #or
       $alphanumeric_string = random_string;  # default length = 20

    Similar to random_string_from, only $range is fixed to
    'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789'.

  rand
       $n = rand;
       #or
       $n = rand($limit);

    Returns a random floating point number from range "[0,1)" (if called without parameter) or
    "[0,$limit)".

  irand
       $i = irand;

    Returns a random unsigned 32bit integer - range "0 .. 0xFFFFFFFF".

## METHODS
  new
       $prng = [Crypt::PRNG](https://www.chedong.com/phpMan.php/perldoc/Crypt%3A%3APRNG/markdown)->new;
       #or
       $prng = [Crypt::PRNG](https://www.chedong.com/phpMan.php/perldoc/Crypt%3A%3APRNG/markdown)->new($alg);
       #or
       $prng = [Crypt::PRNG](https://www.chedong.com/phpMan.php/perldoc/Crypt%3A%3APRNG/markdown)->new($alg, $seed);

       # $alg  ... algorithm name 'Frotuna' (DEFAULT), 'RC4', 'Sober128' or 'Yarrow'
       # $seed ... will be used as an initial entropy for seeding PRNG

    If $seed is not specified the PRNG is automatically seeded with 32bytes random data taken from
    "/dev/random" (UNIX) or "CryptGenRandom" (Win32)

  add_entropy
      $prng->add_entropy($random_data);
      #or
      $prng->add_entropy();

    If called without parameter it uses 32bytes random data taken from "/dev/random" (UNIX) or
    "CryptGenRandom" (Win32).

    BEWARE: you probably do not need this function at all as the module does automatic seeding on
    initialization as well as reseeding after fork and thread creation.

  bytes
       $octets = $prng->bytes($length);

    See random_bytes

  bytes_hex
       $hex_string = $prng->bytes_hex($length);

    See random_bytes_hex

  bytes_b64
       $base64_string = $prng->bytes_b64($length);

    See random_bytes_b64

  bytes_b64u
       $base64url_string = $prng->bytes_b64u($length);

    See random_bytes_b64u

  string
       $alphanumeric_string = $prng->string($length);
       #or
       $alphanumeric_string = $prng->string;

    See random_string

  string_from
       $string = $prng->string_from($range, $length);

    See random_string_from

  double
       $n = $prng->double;
       #or
       $n = $prng->double($limit);

    See rand

  int32
       $i = $prng->int32;

    See irand

## SEE ALSO
    [Crypt::PRNG::Fortuna](https://www.chedong.com/phpMan.php/perldoc/Crypt%3A%3APRNG%3A%3AFortuna/markdown), [Crypt::PRNG::RC4](https://www.chedong.com/phpMan.php/perldoc/Crypt%3A%3APRNG%3A%3ARC4/markdown), [Crypt::PRNG::Sober128](https://www.chedong.com/phpMan.php/perldoc/Crypt%3A%3APRNG%3A%3ASober128/markdown), [Crypt::PRNG::Yarrow](https://www.chedong.com/phpMan.php/perldoc/Crypt%3A%3APRNG%3A%3AYarrow/markdown)