/ 
CryptX-0.088_005
⭐ Starred 36 / Crypt::Mode::OFB

NAME

Crypt::Mode::OFB - Block cipher mode OFB [Output feedback]

SYNOPSIS

use Crypt::Mode::OFB;
my $m = Crypt::Mode::OFB->new('AES');
my $key = '1234567890123456';
my $iv = '1234567890123456';
my $plaintext = 'example plaintext';
my $chunk1 = 'example ';
my $chunk2 = 'plaintext';

# encrypt or decrypt in one call
my $single_ciphertext = $m->encrypt($plaintext, $key, $iv);
my $single_plaintext = $m->decrypt($single_ciphertext, $key, $iv);

# encrypt more chunks
$m->start_encrypt($key, $iv);
my $chunked_ciphertext = '';
$chunked_ciphertext .= $m->add($chunk1);
$chunked_ciphertext .= $m->add($chunk2);

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

DESCRIPTION

This module implements OFB cipher mode. Note: It works only with ciphers from CryptX (Crypt::Cipher::NNNN).

METHODS

Unless noted otherwise, assume $m is an existing mode object created via new, for example:

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

new

my $m = Crypt::Mode::OFB->new($name);
#or
my $m = Crypt::Mode::OFB->new($name, $cipher_rounds);

# $name ............ [string] 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'
#                    or any <NAME> for which there is a Crypt::Cipher::<NAME> module
# $cipher_rounds ... [integer] optional, number of rounds for given cipher

encrypt

Encrypts the plaintext in a single call. Returns the ciphertext as a binary string. The plaintext scalar is converted to bytes using Perl's usual scalar stringification. Defined scalars, including numbers and string-overloaded objects, are accepted. undef is treated as an empty string and may emit Perl's usual "uninitialized value" warning.

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

decrypt

Decrypts the ciphertext in a single call. Returns the plaintext as a binary string. The ciphertext scalar is converted to bytes using Perl's usual scalar stringification. Defined scalars, including numbers and string-overloaded objects, are accepted. undef is treated as an empty string and may emit Perl's usual "uninitialized value" warning.

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

start_encrypt

Initializes encryption mode. Returns the object itself.

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

start_decrypt

Initializes decryption mode. Returns the object itself.

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

add

Feeds data to the encryption or decryption stream. Returns a binary string.

Each argument is converted to bytes using Perl's usual scalar stringification. Defined scalars, including numbers and string-overloaded objects, are accepted. undef is treated as an empty string and may emit Perl's usual "uninitialized value" warning.

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

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

finish

OFB is a streaming mode and does not use padding, so finish returns an empty string. It exists for API consistency with Crypt::Mode::CBC and Crypt::Mode::ECB and may be safely called or omitted.

$m->start_encrypt($key, $iv);
my $ciphertext = '';
$ciphertext .= $m->add($chunk1);
$ciphertext .= $m->add($chunk2);
$ciphertext .= $m->finish;   # returns ''

SEE ALSO