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);

        # $cipher_name .. one of 'AES', 'Anubis', 'Blowfish', 'CAST5', 'Camellia', 'DES', 'DES_EDE',
        #                 'KASUMI', 'Khazad', 'MULTI2', 'Noekeon', 'RC2', 'RC5', 'RC6',
        #                 'SAFERP', 'SAFER_K128', 'SAFER_K64', 'SAFER_SK128', 'SAFER_SK64',
        #                 'SEED', 'Skipjack', 'Twofish', 'XTEA', 'IDEA', 'Serpent'
        #                 simply any <NAME> for which there exists Crypt::Cipher::<NAME>
        # $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
          $m->start_encrypt($key, $iv);

   start_decrypt
          $m->start_decrypt($key, $iv);

   add
          # in encrypt mode
          my $plaintext = $m->add($ciphertext);

          # in decrypt mode
          my $ciphertext = $m->add($plaintext);

SEE ALSO

       •   CryptX, Crypt::Cipher

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

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