package Crypt::KeyDerivation;

use strict;
use warnings;

require Exporter; our @ISA = qw(Exporter); ### use Exporter 'import';
our %EXPORT_TAGS = ( all => [qw(pbkdf1 pbkdf2 hkdf hkdf_expand hkdf_extract)] );
our @EXPORT_OK = ( @{ $EXPORT_TAGS{'all'} } );
our @EXPORT = qw();

use CryptX;
use Crypt::Digest;

sub pbkdf1 {
  my ($password, $salt, $iteration_count, $hash_name, $len) = @_;
  $iteration_count ||= 5000;
  $hash_name = Crypt::Digest::_trans_digest_name($hash_name||'SHA256');
  $len ||= 32;
  return _pkcs_5_alg1($password, $salt, $iteration_count, $hash_name, $len);
}

sub pbkdf2 {
  my ($password, $salt, $iteration_count, $hash_name, $len) = @_;
  $iteration_count ||= 5000;
  $hash_name = Crypt::Digest::_trans_digest_name($hash_name||'SHA256');
  $len ||= 32;
  return _pkcs_5_alg2($password, $salt, $iteration_count, $hash_name, $len);
}

sub hkdf_extract {
  # RFC: HKDF-Extract(salt, IKM, [Hash]) -> PRK
  #my ($hash_name, $salt, $keying_material) = @_;
  my ($keying_material, $salt, $hash_name) = @_;
  $hash_name = Crypt::Digest::_trans_digest_name($hash_name||'SHA256');
  $salt = pack("H*", "00" x Crypt::Digest->hashsize($hash_name)) unless defined $salt; # according to rfc5869 defaults to HashLen zero octets
  return _hkdf_extract($hash_name, $salt, $keying_material);
}

sub hkdf_expand {
  # RFC: HKDF-Expand(PRK, info, L, [Hash]) -> OKM
  #my ($hash_name, $info, $keying_material, $len) = @_;
  my ($keying_material, $hash_name, $len, $info) = @_;
  $len ||= 32;
  $info ||= '';
  $hash_name = Crypt::Digest::_trans_digest_name($hash_name||'SHA256');
  return _hkdf_expand($hash_name, $info, $keying_material, $len);
}

sub hkdf {
  #my ($hash_name, $salt, $info, $keying_material, $len) = @_;
  my ($keying_material, $salt, $hash_name, $len, $info) = @_;
  $len ||= 32;
  $info ||= '';
  $hash_name = Crypt::Digest::_trans_digest_name($hash_name||'SHA256');
  $salt = pack("H*", "00" x Crypt::Digest->hashsize($hash_name)) unless defined $salt; # according to rfc5869 defaults to HashLen zero octets
  return _hkdf($hash_name, $salt, $info, $keying_material, $len);
}

1;

=pod

=head1 NAME

Crypt::KeyDerivation - PBKDF1, PBKFD2 and HKDF key derivation functions

=head1 SYNOPSIS

  ### PBKDF1/2
  $derived_key1 = pbkdf1($password, $salt, $iteration_count, $hash_name, $len);
  $derived_key2 = pbkdf2($password, $salt, $iteration_count, $hash_name, $len);

  ### HKDF & co.
  $derived_key3 = hkdf($keying_material, $salt, $hash_name, $len, $info);
  $prk  = hkdf_extract($keying_material, $salt, $hash_name);
  $okm1 = hkdf_expand($prk, $hash_name, $len, $info);

=head1 DESCRIPTION

Provides an interface to Key derivation functions:

=over

=item * PBKFD1 and PBKDF according to PKCS#5 v2.0 L<https://tools.ietf.org/html/rfc2898|https://tools.ietf.org/html/rfc2898>

=item * HKDF (+ related) according to L<https://tools.ietf.org/html/rfc5869|https://tools.ietf.org/html/rfc5869>

=back

=head1 FUNCTIONS

=head2 pbkdf1

B<BEWARE:> if you are not sure, do not use C<pbkdf1> but rather choose C<pbkdf2>.

  $derived_key = pbkdf1($password, $salt, $iteration_count, $hash_name, $len);
  #or
  $derived_key = pbkdf1($password, $salt, $iteration_count, $hash_name);
  #or
  $derived_key = pbkdf1($password, $salt, $iteration_count);
  #or
  $derived_key = pbkdf1($password, $salt);

  # $password ......... input keying material  (password)
  # $salt ............. salt/nonce (expected length: 8)
  # $iteration_count .. optional, DEFAULT: 5000
  # $hash_name ........ optional, DEFAULT: 'SHA256'
  # $len .............. optional, derived key len, DEFAULT: 32

=head2 pbkdf2

  $derived_key = pbkdf2($password, $salt, $iteration_count, $hash_name, $len);
  #or
  $derived_key = pbkdf2($password, $salt, $iteration_count, $hash_name);
  #or
  $derived_key = pbkdf2($password, $salt, $iteration_count);
  #or
  $derived_key = pbkdf2($password, $salt);

  # $password ......... input keying material (password)
  # $salt ............. salt/nonce
  # $iteration_count .. optional, DEFAULT: 5000
  # $hash_name ........ optional, DEFAULT: 'SHA256'
  # $len .............. optional, derived key len, DEFAULT: 32

=head2 hkdf

  $okm2 = hkdf($password, $salt, $hash_name, $len, $info);
  #or
  $okm2 = hkdf($password, $salt, $hash_name, $len);
  #or
  $okm2 = hkdf($password, $salt, $hash_name);
  #or
  $okm2 = hkdf($password, $salt);

  # $password ... input keying material (password)
  # $salt ....... salt/nonce, if undef defaults to HashLen zero octets
  # $hash_name .. optional, DEFAULT: 'SHA256'
  # $len ........ optional, derived key len, DEFAULT: 32
  # $info ....... optional context and application specific information, DEFAULT: ''

=head2 hkdf_extract

  $prk  = hkdf_extract($password, $salt, $hash_name);
  #or
  $prk  = hkdf_extract($password, $salt, $hash_name);

  # $password ... input keying material (password)
  # $salt ....... salt/nonce, if undef defaults to HashLen zero octets
  # $hash_name .. optional, DEFAULT: 'SHA256'


=head2 hkdf_expand

  $okm = hkdf_expand($pseudokey, $hash_name, $len, $info);
  #or
  $okm = hkdf_expand($pseudokey, $hash_name, $len);
  #or
  $okm = hkdf_expand($pseudokey, $hash_name);
  #or
  $okm = hkdf_expand($pseudokey);

  # $pseudokey .. input keying material
  # $hash_name .. optional, DEFAULT: 'SHA256'
  # $len ........ optional, derived key len, DEFAULT: 32
  # $info ....... optional context and application specific information, DEFAULT: ''
