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        # $cipher_name .. one of 'AES', 'Anubis', 'Blowfish', 'CAST5', 'Camellia', 'DES', 'DES_EDE',
39        #                 'KASUMI', 'Khazad', 'MULTI2', 'Noekeon', 'RC2', 'RC5', 'RC6',
40        #                 'SAFERP', 'SAFER_K128', 'SAFER_K64', 'SAFER_SK128', 'SAFER_SK64',
41        #                 'SEED', 'Skipjack', 'Twofish', 'XTEA', 'IDEA', 'Serpent'
42        #                 simply any <NAME> for which there exists Crypt::Cipher::<NAME>
43        # $ctr_mode ..... 0 little-endian counter (DEFAULT)
44        #                 1 big-endian counter
45        #                 2 little-endian + RFC3686 incrementing
46        #                 3 big-endian + RFC3686 incrementing
47        # $ctr_width .... counter width in bytes (DEFAULT = full block width)
48        # $cipher_rounds ... optional num of rounds for given cipher
49
50   encrypt
51          my $ciphertext = $m->encrypt($plaintext, $key, $iv);
52
53   decrypt
54          my $plaintext = $m->decrypt($ciphertext, $key, $iv);
55
56   start_encrypt
57          $m->start_encrypt($key, $iv);
58
59   start_decrypt
60          $m->start_decrypt($key, $iv);
61
62   add
63          # in encrypt mode
64          my $plaintext = $m->add($ciphertext);
65
66          # in decrypt mode
67          my $ciphertext = $m->add($plaintext);
68

SEE ALSO

70       •   CryptX, Crypt::Cipher
71
72       •   Crypt::Cipher::AES, Crypt::Cipher::Blowfish, ...
73
74       •   <https://en.wikipedia.org/wiki/Block_cipher_mode_of_operation#Counter_.28CTR.29>
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78perl v5.36.1                      2023-10-04               Crypt::Mode::CTR(3)
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