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.\" ========================================================================
.\"
.IX Title "Crypt::Mode::CBC 3pm"
.TH Crypt::Mode::CBC 3pm "2020-11-09" "perl v5.32.0" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
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.SH "NAME"
Crypt::Mode::CBC \- Block cipher mode CBC [Cipher\-block chaining]
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 2
\&   use Crypt::Mode::CBC;
\&   my $m = Crypt::Mode::CBC\->new(\*(AqAES\*(Aq);
\&
\&   #(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(\*(Aqsome data\*(Aq);
\&   $ciphertext .= $m\->add(\*(Aqmore data\*(Aq);
\&   $ciphertext .= $m\->finish;
\&
\&   #decrypt more chunks
\&   $m\->start_decrypt($key, $iv);
\&   my $plaintext = $m\->add($some_ciphertext);
\&   $plaintext .= $m\->add($more_ciphertext);
\&   $plaintext .= $m\->finish;
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
This module implements \s-1CBC\s0 cipher mode. \fB\s-1NOTE:\s0\fR it works only with ciphers from CryptX (Crypt::Cipher::NNNN).
.SH "METHODS"
.IX Header "METHODS"
.SS "new"
.IX Subsection "new"
.Vb 5
\& 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 ....... one of \*(AqAES\*(Aq, \*(AqAnubis\*(Aq, \*(AqBlowfish\*(Aq, \*(AqCAST5\*(Aq, \*(AqCamellia\*(Aq, \*(AqDES\*(Aq, \*(AqDES_EDE\*(Aq,
\& #               \*(AqKASUMI\*(Aq, \*(AqKhazad\*(Aq, \*(AqMULTI2\*(Aq, \*(AqNoekeon\*(Aq, \*(AqRC2\*(Aq, \*(AqRC5\*(Aq, \*(AqRC6\*(Aq,
\& #               \*(AqSAFERP\*(Aq, \*(AqSAFER_K128\*(Aq, \*(AqSAFER_K64\*(Aq, \*(AqSAFER_SK128\*(Aq, \*(AqSAFER_SK64\*(Aq,
\& #               \*(AqSEED\*(Aq, \*(AqSkipjack\*(Aq, \*(AqTwofish\*(Aq, \*(AqXTEA\*(Aq, \*(AqIDEA\*(Aq, \*(AqSerpent\*(Aq
\& #               simply any <NAME> for which there exists Crypt::Cipher::<NAME>
\& # $padding .... 0 no padding (plaintext size has to be multiple of block length)
\& #               1 PKCS5 padding, Crypt::CBC\*(Aqs "standard" \- DEFAULT
\& #               2 Crypt::CBC\*(Aqs "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 ... optional num of rounds for given cipher
.Ve
.SS "encrypt"
.IX Subsection "encrypt"
.Vb 1
\&   my $ciphertext = $m\->encrypt($plaintext, $key, $iv);
.Ve
.SS "decrypt"
.IX Subsection "decrypt"
.Vb 1
\&   my $plaintext = $m\->decrypt($ciphertext, $key, $iv);
.Ve
.SS "start_encrypt"
.IX Subsection "start_encrypt"
.Vb 1
\&   $m\->start_encrypt($key, $iv);
.Ve
.SS "start_decrypt"
.IX Subsection "start_decrypt"
.Vb 1
\&   $m\->start_decrypt($key, $iv);
.Ve
.SS "add"
.IX Subsection "add"
.Vb 2
\&   # in encrypt mode
\&   my $plaintext = $m\->add($ciphertext);
\&
\&   # in decrypt mode
\&   my $ciphertext = $m\->add($plaintext);
.Ve
.SS "finish"
.IX Subsection "finish"
.Vb 6
\&   #encrypt more chunks
\&   $m\->start_encrypt($key, $iv);
\&   my $ciphertext = \*(Aq\*(Aq;
\&   $ciphertext .= $m\->add(\*(Aqsome data\*(Aq);
\&   $ciphertext .= $m\->add(\*(Aqmore data\*(Aq);
\&   $ciphertext .= $m\->finish;
\&
\&   #decrypt more chunks
\&   $m\->start_decrypt($key, $iv);
\&   my $plaintext = \*(Aq\*(Aq;
\&   $plaintext .= $m\->add($some_ciphertext);
\&   $plaintext .= $m\->add($more_ciphertext);
\&   $plaintext .= $m\->finish;
.Ve
.SH "SEE ALSO"
.IX Header "SEE ALSO"
.IP "\(bu" 4
CryptX, Crypt::Cipher
.IP "\(bu" 4
Crypt::Cipher::AES, Crypt::Cipher::Blowfish, ...
.IP "\(bu" 4
<https://en.wikipedia.org/wiki/Block_cipher_mode_of_operation#Cipher\-block_chaining_.28CBC.29>