ECB(3) User Contributed Perl Documentation ECB(3)NAMECrypt::ECB - Encrypt Data using ECB Mode
SYNOPSIS
Use Crypt::ECB OO style
use Crypt::ECB;
$crypt = Crypt::ECB->new;
$crypt->padding(PADDING_AUTO);
$crypt->cipher('Blowfish') || die $crypt->errstring;
$crypt->key('some_key');
$enc = $crypt->encrypt("Some data.");
print $crypt->decrypt($enc);
or use the function style interface
use Crypt::ECB qw(encrypt decrypt encrypt_hex decrypt_hex);
$ciphertext = encrypt($key, 'Blowfish', "Some data", PADDING_AUTO);
$plaintext = decrypt($key, 'Blowfish', $ciphertext, PADDING_AUTO);
$hexcode = encrypt_hex($key, $cipher, $plaintext);
$plain = decrypt_hex($key, $cipher, $hexcode);
DESCRIPTION
This module is a Perl-only implementation of the ECB mode. In combina-
tion with a block cipher such as DES, IDEA or Blowfish, you can encrypt
and decrypt messages of arbitrarily long length. Though for security
reasons other modes than ECB such as CBC should be preferred. See
textbooks on cryptography if you want to know why.
The functionality of the module can be accessed via OO methods or via
standard function calls. Remember that some crypting module like for
example Blowfish has to be installed. The syntax follows that of
Crypt::CBC.
METHODSnew(), key(), cipher(), padding()
$crypt = Crypt::ECB->new;
$crypt->key('Some_key');
$crypt->cipher('Blowfish') || die $crypt->errstring;
$crypt->padding(PADDING_AUTO);
print $crypt->key;
print $crypt->cipher;
print $crypt->padding;
$crypt = Crypt::ECB->new('Some_key','Blowfish');
$crypt->cipher || die "'Blowfish' wasn't loaded for some reason.";
new() initializes the variables it uses. Optional parameters are key
and cipher. If called without parameters you have to call key() and
cipher() before you can start crypting. If called with key but without
cipher, for compatibility with Crypt::CBC 'DES' is assumed.
key() sets the key if given a parameter. It always returns the key.
Note that some crypting modules require keys of definite length. For
example the Crypt::Blowfish module expects an eight byte key.
cipher() sets the block cipher to be used if given a parameter. It
tries to load the corresponding module. If an error occurs, it returns
0 and sets $crypt->{Errstring}. Otherwise it returns the cipher name.
Free packages available for Perl are for example Blowfish, DES or IDEA.
If called without parameter it just returns the name of the cipher.
padding() sets the way how data is padded up to a multiple of the
cipher's blocksize. Until now two ways are implemented: When set to
PADDING_NONE, no padding is done. You then have to take care of correct
padding (and truncating) yourself. When set to PADDING_AUTO, the ECB
module handles padding (and truncating when decrypting) the same way
Crypt::CBC does.
By default the padding style is set to PADDING_NONE. This means if you
don't bother and your data has not the correct length, the module will
complain and therefore force you to think about what you really want.
start(), mode(), crypt(), finish()
$crypt->start('encrypt') || die $crypt->errstring;
$enc .= $crypt->crypt($_) foreach (@lines);
$enc .= $crypt->finish;
$crypt->start('decrypt');
print $crypt->mode;
start() sets the crypting mode and checks if all required variables
like key and cipher are set. Allowed parameters are any words starting
either with 'e' or 'd'. The Method returns the mode which is set or 0
if an error occurred.
mode() is called without parameters and just returns the mode which is
set.
crypt() processes the data given as argument. If called without argu-
ment $_ is processed. The method returns the processed data. Cipher
and key have to be set in order to be able to process data. If some of
these are missing or start() was not called before, the method dies.
After having sent all data to be processed to crypt() you have to call
finish() in order to flush data that's left in the buffer.
caching()
$crypt->caching(1); # caching on
$crypt->caching(0); # caching off
print $crypt->caching;
The caching mode is returned. If given an argument caching mode is set.
Caching is on if caching() evaluates true, otherwise caching is off.
By default caching is on.
What is this caching? The Crypt::ECB module communicates with the
cipher module via some object. Creating the cipher object takes some
time for the cipher module has to do some initialization. Now caching
means that the same cipher object is used until caching is turned off
or the key or the cipher module are changed. If caching is off, a new
cipher object is created is created each time crypt() or finish() are
called and destroyed at the end of these methods. Crypting using
caching is much faster than without caching.
encrypt(), decrypt(), encrypt_hex(), decrypt_hex()
$enc = $crypt->encrypt($data);
print $crypt->decrypt($enc);
$hexenc = $crypt->encrypt_hex($data);
print $crypt->decrypt_hex($hexenc);
encrypt() and decrypt() are convenience methods which call start(),
crypt() and finish() for you.
encrypt_hex() and decrypt_hex() are convenience functions that operate
on ciphertext in a hexadecimal representation. They are exactly equiva-
lent to
$hexenc = join('',unpack('H*',$crypt->encrypt($data)));
print $crypt->decrypt(pack('H*',$hexenc));
These functions can be useful if, for example, you wish to place the
encrypted information into an e-mail message, Web page or URL.
errstring()
print $crypt->errstring;
Some methods like cipher() or start() return 0 if an error occurs. You
can then retrieve a more detailed error message by calling
$crypt->errstring.
VARIABLES
Variables which could be of interest to the outside world are:
$crypt->{Key},
$crypt->{Cipher},
$crypt->{Module},
$crypt->{Keysize},
$crypt->{Blocksize},
$crypt->{Mode},
$crypt->{Caching},
$crypt->{Padding},
$crypt->{Errstring}.
The variables should not be set directly, use instead the above
described methods. Reading should not pose a problem.
CONSTANTS
The two constants naming the padding styles are exported by default:
PADDING_NONE => 0
PADDING_AUTO => 1
FUNCTIONS
For convenience en- or decrypting can also be done by calling ordinary
functions. The functions are: encrypt(), decrypt(), encrypt_hex,
decrypt_hex. The module is smart enough to recognize whether these
functions are called in an OO context or not.
encrypt(), decrypt(), encrypt_hex(), decrypt_hex()
$ciphertext = encrypt($key, $cipher, $plaintext, PADDING_AUTO);
$plaintext = decrypt($key, $cipher, $ciphertext, PADDING_AUTO);
$ciphertext = encrypt_hex($key, $cipher, $plaintext, PADDING_AUTO);
$plaintext = decrypt_hex($key, $cipher, $ciphertext, PADDING_AUTO);
encrypt() and decrypt() process the provided text and return either the
corresponding ciphertext (encrypt) or plaintext (decrypt). Data and
padstyle are optional, but remember that by default no padding is done.
If data is omitted, $_ is assumed.
encrypt_hex() and decrypt_hex() operate on ciphertext in a hexadecimal
representation. Otherwise usage is the same as for encrypt() and
decrypt().
BUGS
None that I know of.
TODO
The other block cipher modes CBC, CFB and OFB could be implemented.
Convenience encrypt and decrypt functions utilizing base64 encoding
could be added.
COPYING
This program is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by the
Free Software Foundation; either version 2 of the License, or (at your
option) any later version.
This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of MER-
CHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
Public License for more details.
You should have received a copy of the GNU General Public License along
with this program; if not, write to the Free Software Foundation, Inc.,
59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
AUTHOR
Christoph Appel (see ECB.pm for email address)
SEE ALSOperl(1), Crypt::DES(3), Crypt::IDEA(3), Crypt::CBC(3)perl v5.8.8 2005-01-07 ECB(3)
