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.\"
.IX Title "Crypt::Mode::CFB 3"
.TH Crypt::Mode::CFB 3 "2022-01-07" "perl v5.26.3" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
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.SH "NAME"
Crypt::Mode::CFB \- Block cipher mode CFB [Cipher feedback]
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 2
\&   use Crypt::Mode::CFB;
\&   my $m = Crypt::Mode::CFB\->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);
\&
\&   #decrypt more chunks
\&   $m\->start_decrypt($key, $iv);
\&   my $plaintext = $m\->add($some_ciphertext);
\&   $plaintext .= $m\->add($more_ciphertext);
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
This module implements \s-1CFB\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 3
\& my $m = Crypt::Mode::CFB\->new($name);
\& #or
\& my $m = Crypt::Mode::CFB\->new($name, $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>
\& # $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
.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_feedback_.28CFB.29>