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| Crypt::Mode::CBC(3) | User Contributed Perl Documentation | Crypt::Mode::CBC(3) |
NAME¶
Crypt::Mode::CBC - Block cipher mode CBC [Cipher-block chaining]
SYNOPSIS¶
use Crypt::Mode::CBC;
my $m = Crypt::Mode::CBC->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);
$chunked_ciphertext .= $m->finish;
# decrypt more chunks
$m->start_decrypt($key, $iv);
my $chunked_plaintext = '';
$chunked_plaintext .= $m->add($chunked_ciphertext);
$chunked_plaintext .= $m->finish;
DESCRIPTION¶
This module implements CBC 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::CBC->new('AES');
new¶
my $m = Crypt::Mode::CBC->new($name); #or my $m = Crypt::Mode::CBC->new($name, $padding); #or my $m = Crypt::Mode::CBC->new($name, $padding, $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 # $padding .... [integer] 0 no padding (plaintext size has to be multiple of block length) # 1 PKCS5 padding, Crypt::CBC's "standard" - DEFAULT # 2 Crypt::CBC's "oneandzeroes" # 3 ANSI X.923 padding # 4 zero padding # 5 zero padding (+a block of zeros if the output length is divisible by the blocksize) # $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¶
Finalizes the stream. In encryption mode, pads and encrypts the final block; in decryption mode, decrypts and removes padding from the final block. Returns the result as a binary string (may be empty if there is no data to flush).
# encrypt more chunks $m->start_encrypt($key, $iv); my $chunk1 = 'example '; my $chunk2 = 'plaintext'; my $ciphertext = ''; $ciphertext .= $m->add($chunk1); $ciphertext .= $m->add($chunk2); $ciphertext .= $m->finish; # decrypt more chunks $m->start_decrypt($key, $iv); my $plaintext = ''; $plaintext .= $m->add($ciphertext); $plaintext .= $m->finish;
SEE ALSO¶
- CryptX, Crypt::Cipher
- Crypt::Cipher::AES, Crypt::Cipher::Blowfish, ...
- <https://en.wikipedia.org/wiki/Block_cipher_mode_of_operation#Cipher-block_chaining_.28CBC.29>
| 2026-05-11 | perl v5.42.1 |