NAME

Crypt::ScryptKDF - Scrypt password based key derivation function

SYNOPSIS

Creating / verifying scrypt-based password hash:

 use Crypt::ScryptKDF qw(scrypt_hash scrypt_hash_verify);

 my $hash1 = scrypt_hash("secret password");
 # .. later
 die "Invalid password" unless scrypt_hash_verify("secret password", $hash1);

 #or by specifying Scrypt parameters
 my $hash2 = scrypt_hash("secret password", \32, 16384, 8, 1, 32);
 # .. later
 die "Invalid password" unless scrypt_hash_verify("secret password", $hash2);

Creating raw scrypt-based derived key:

 use Crypt::ScryptKDF qw(scrypt_raw scrypt_hex scrypt_b64);

 my $binary_buffer = scrypt_raw($password, $salt, $N, $r, $p, $len);
 my $hexadecimal_string = scrypt_hex($password, $salt, $N, $r, $p, $len);
 my $base64_string = scrypt_b64($password, $salt, $N, $r, $p, $len);

DESCRIPTION

Scrypt is a password-based key derivation function (like for example PBKDF2). Scrypt was designed to be "memory-hard" algorithm in order to make it expensive to perform large scale custom hardware attacks.

It can be used for:

• deriving cryptographic keys from low-entropy password (like PBKDF2)

• creating (+validating) password hashes (like PBKDF2 or Bcrypt)

More details about Scrypt: http://www.tarsnap.com/scrypt/scrypt.pdf and https://tools.ietf.org/html/draft-josefsson-scrypt-kdf

IMPORTANT: This module needs a cryptographically strong random number generator. It tries to use one of the following:

• Crypt::PRNG - random_bytes()

• Crypt::OpenSSL::Random - random_bytes()

• Net::SSLeay - RAND_bytes()

• Crypt::Random - makerandom_octet()

• Bytes::Random::Secure - random_bytes()

• As an unsecure fallback it uses built-in rand()

FUNCTIONS

• scrypt_raw

  Derive a key from given password and salt (+ optional params).

   my $derived_key_raw_bytes = scrypt_raw($password, $salt, $N, $r, $p, $len);
   #or
   my $derived_key_raw_bytes = scrypt_raw($password, $salt);
  
   #  $password - low-entropy secret (bytes)
   #  $salt - raw octects (bytes) with a salt
   #  $N - CPU/memory cost (has to be power of 2 and >1) DEFAULT: 2^14 = 16384
   #  $r - block size parameter                          DEFAULT: 8
   #  $p - parallelization parameter                     DEFAULT: 1
   #  $len - length of derived key (in bytes)            DEFAULT: 32
   #returns:
   #  $derived_key .. raw bytes of length $len

• scrypt_hex

  Similar to scrypt_raw only the return value is encoded as hexadecimal value.

   my $derived_key_hex_string = scrypt_hex($password, $salt, $N, $r, $p, $len);
   #or
   my $derived_key_hex_string = scrypt_hex($password, $salt);

• scrypt_b64

  Similar to scrypt_raw only the return value is BASE64 encoded.

   my $derived_key_base64_string = scrypt_b64($password, $salt, $N, $r, $p, $len);
   #or
   my $derived_key_base64_string = scrypt_b64($password, $salt);

• scrypt_hash

  Create a password hash for given password.

   my $hash = scrypt_hash($password, $salt, $N, $r, $p, $len);
  
   #  params same as by scrypt_raw, the $salt can also be a scalar ref with salt
   #  length e.g. $salt=\24 means that salt will be 24 randomly generated bytes
   #returns:
   #  string with password hash (suitable for storing in DB) e.g.
   #  'SCRYPT:16384:8:1:BK8jkrqgm3BEtMh/g+WGL+k8ZeoAo=:YsEnQWld4UK8EqRZ9JuGbQnnlkXaM='

  Some of the parameters are optional:

   # 1 arg variant
   my $hash = scrypt_hash($password); # generate random salt (32 bytes)
  
   # 2 args variant
   my $hash = scrypt_hash($password, $salt); # use given $salt
   my $hash = scrypt_hash($password, \20);   # generate random salt (20 bytes)
  
   # 5 args variant
   my $hash = scrypt_hash($password, $N, $r, $p, $len); # random salt (32 bytes)

• scrypt_hash_verify

  Verify a password hash created with scrypt_hash()

   my $is_valid = scrypt_hash_verify($password, $hash);
   #  $password - password to be verified
   #  $hash - hash previously created via scrypt_hash
   #returns:
   #  1 (ok) or 0 (fail)

• random_bytes

  Generate random bytes of given length.

   my $salt = random_bytes($len);
   #  $len - number of random bytes
   #returns:
   #  $len random octets

LICENSE

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

COPYRIGHT

Copyright (c) 2013-2015 DCIT, a.s. http://www.dcit.cz / Karel Miko