1Crypt::Mode::CTR(3)   User Contributed Perl Documentation  Crypt::Mode::CTR(3)
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NAME

6       Crypt::Mode::CTR - Block cipher mode CTR [Counter mode]
7

SYNOPSIS

9          use Crypt::Mode::CTR;
10          my $m = Crypt::Mode::CTR->new('AES');
11
12          #(en|de)crypt at once
13          my $ciphertext = $m->encrypt($plaintext, $key, $iv);
14          my $plaintext = $m->decrypt($ciphertext, $key, $iv);
15
16          #encrypt more chunks
17          $m->start_encrypt($key, $iv);
18          my $ciphertext = $m->add('some data');
19          $ciphertext .= $m->add('more data');
20
21          #decrypt more chunks
22          $m->start_decrypt($key, $iv);
23          my $plaintext = $m->add($some_ciphertext);
24          $plaintext .= $m->add($more_ciphertext);
25

DESCRIPTION

27       This module implements CTR cipher mode. NOTE: it works only with
28       ciphers from CryptX (Crypt::Cipher::NNNN).
29

METHODS

31   new
32        my $m = Crypt::Mode::CTR->new($cipher_name);
33        #or
34        my $m = Crypt::Mode::CTR->new($cipher_name, $ctr_mode, $ctr_width);
35        #or
36        my $m = Crypt::Mode::CTR->new($cipher_name, $ctr_mode, $ctr_width, $cipher_rounds);
37
38        # $ctr_mode .... 0 little-endian counter (DEFAULT)
39        #                1 big-endian counter
40        #                2 little-endian + RFC3686 incrementing
41        #                3 big-endian + RFC3686 incrementing
42        # $ctr_width ... counter width in bytes (DEFAULT = full block width)
43        # $cipher_rounds ... optional num of rounds for given cipher
44
45   encrypt
46          my $ciphertext = $m->encrypt($plaintext, $key, $iv);
47
48   decrypt
49          my $plaintext = $m->decrypt($ciphertext, $key, $iv);
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51   start_encrypt
52          $m->start_encrypt($key, $iv);
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54   start_decrypt
55          $m->start_decrypt($key, $iv);
56
57   add
58          # in encrypt mode
59          my $plaintext = $m->add($ciphertext);
60
61          # in decrypt mode
62          my $ciphertext = $m->add($plaintext);
63

SEE ALSO

65       ·   CryptX, Crypt::Cipher
66
67       ·   Crypt::Cipher::AES, Crypt::Cipher::Blowfish, ...
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69       ·   <https://en.wikipedia.org/wiki/Block_cipher_mode_of_operation#Counter_.28CTR.29>
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73perl v5.28.0                      2017-09-15               Crypt::Mode::CTR(3)
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