Crypt::Ctr - Encrypt Data in Counter Mode
use Crypt::Ctr; my $cipher = new Crypt::Ctr $key, 'Crypt::Rijndael'; my $ciphertext = $cipher->encrypt($plaintext); my $plaintext = $cipher->decrypt($ciphertext); my $cipher2 = new Crypt::Ctr $key, 'Digest::MD5'; $ciphertext = $cipher->encrypt($plaintext); $plaintext = $cipher->decrypt($ciphertext);
Generic Counter Mode implementation in pure Perl. The Counter Mode module constructs a stream cipher from a block cipher or cryptographic hash funtion and returns it as an object. Any block cipher in the Crypt:: class can be used, as long as it supports the blocksize and keysize methods. Any hash function in the Digest:: class can be used, as long as it supports the add method.
Crypt::
blocksize
keysize
Digest::
add
Counter mode produces the keystream independent from the input. Be sure not to re-use keys in Counter mode. As with Cipher Feedback mode, one should use Counter mode inside authenticated channels, e.g. HMAC.
$cipher = new Crypt::Ctr $key, $algorithm
Constructs a Crypt::Ctr object. If $algorithm is a block cipher, then $key should be of the correct size for that cipher. In most cases you can inquire the block cipher module by invoking the keysize method. If $algorithm is a hash function, then $key can be of any size.
$algorithm
$key
$ciphertext = $cipher->encrypt $plaintext
Encrypts $plaintext. The input is XORed with the keystream generated from the internal state of the Ctr object and that state is updated with the output. $plaintext can be of any length.
$plaintext
$cipher->reset
Resets the internal state. Remember to do that before decrypting, if you use the same object.
$plaintext = $cipher->decrypt $ciphertext
Decrypts $ciphertext.
$ciphertext
This is awfully slow. Some classes in Digest:: do not provide the add method, so they will fail. The internal counter is a Perl integer. This could possibly lead to strange errors when encrypting more than POSIX::LONG_MAX bytes and decrypting it on a different architecture.
POSIX::LONG_MAX
Matthias Bauer <matthiasb@acm.org>
To install Crypt::Ctr, copy and paste the appropriate command in to your terminal.
cpanm
cpanm Crypt::Ctr
CPAN shell
perl -MCPAN -e shell install Crypt::Ctr
For more information on module installation, please visit the detailed CPAN module installation guide.