NAME

Crypt::Mode::CTR - Block cipher mode CTR [Counter mode]

SYNOPSIS

   use Crypt::Mode::CTR;
   my $m = Crypt::Mode::CTR->new('AES');

   #(en|de)crypt at once
   my $ciphertext = $m->encrypt($plaintext, $key, $iv);
   my $plaintext = $m->decrypt($ciphertext, $key, $iv);

   #encrypt more chunks
   $m->start_encrypt($key, $iv);
   my $ciphertext = $m->add('some data');
   $ciphertext .= $m->add('more data');

   #decrypt more chunks
   $m->start_decrypt($key, $iv);
   my $plaintext = $m->add($some_ciphertext);
   $plaintext .= $m->add($more_ciphertext);

DESCRIPTION

This module implements CTR cipher mode. NOTE: it works only with ciphers from CryptX (Crypt::Cipher::NNNN).

METHODS

new

 my $m = Crypt::Mode::CTR->new($cipher_name);
 #or
 my $m = Crypt::Mode::CTR->new($cipher_name, $ctr_mode, $ctr_width);
 #or
 my $m = Crypt::Mode::CTR->new($cipher_name, $ctr_mode, $ctr_width, $cipher_rounds);

 # $ctr_mode .... 0 little-endian counter (DEFAULT)
 #                1 big-endian counter
 #                2 little-endian + RFC3686 incrementing
 #                3 big-endian + RFC3686 incrementing
 # $ctr_width ... counter width in bytes (DEFAULT = full block width)
 # $cipher_rounds ... optional num of rounds for given cipher

encrypt

   my $ciphertext = $m->encrypt($plaintext, $key, $iv);

decrypt

   my $plaintext = $m->decrypt($ciphertext, $key, $iv);

start_encrypt

See example below "finish".

start_decrypt

See example below "finish".

add

See example below "finish".

finish

   #encrypt more chunks
   $m->start_encrypt($key, $iv);
   my $ciphertext = '';
   $ciphertext .= $m->add('some data');
   $ciphertext .= $m->add('more data');

   #decrypt more chunks
   $m->start_decrypt($key, $iv);
   my $plaintext = '';
   $plaintext .= $m->add($some_ciphertext);
   $plaintext .= $m->add($more_ciphertext);

SEE ALSO

• CryptX, Crypt::Cipher

• Crypt::Cipher::AES, Crypt::Cipher::Blowfish, ...

• https://en.wikipedia.org/wiki/Block_cipher_mode_of_operation#Counter_.28CTR.29