chromatic > Crypt-CipherSaber > Crypt::CipherSaber

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Module Version: 1.00   Source  

NAME ^

Crypt::CipherSaber - Perl module implementing CipherSaber encryption.

SYNOPSIS ^

  use Crypt::CipherSaber;
  my $cs = Crypt::CipherSaber->new('my pathetic secret key');

  my $coded = $cs->encrypt('Here is a secret message for you');
  my $decoded = $cs->decrypt($coded);

  # encrypt from and to a file
  open(INFILE, 'secretletter.txt') or die "Can't open infile: $!";
  open(OUTFILE, '>secretletter.cs1') or die "Can't open outfile: $!";
  binmode(INFILE);
  binmode(OUTFILE);
  $cs->fh_crypt(\*INFILE, \*OUTFILE, 1);

  # decrypt from and to a file
  open(INFILE, 'secretletter.cs1') or die "Can't open infile: $!";
  open(OUTFILE, '>secretletter.txt') or die "Can't open outfile: $!";
  binmode(INFILE);
  binmode(OUTFILE);
  $cs->fh_crypt(\*INFILE, \*OUTFILE);

DESCRIPTION ^

The Crypt::CipherSaber module implements CipherSaber encryption, described at http://ciphersaber.gurus.com/. It is simple, fairly speedy, and relatively secure algorithm based on RC4.

Encryption and decryption are done based on a secret key, which must be shared with all intended recipients of a message.

METHODS ^

new($key, $N)

Initialize a new Crypt::CipherSaber object. $key is a required parameter: the key used to encrypt or to decrypt messages. $N is optional. If provided and greater than one, it causes the object to use CipherSaber-2 encryption (slightly slower but more secure). If not specified, or equal to 1, the module defaults to CipherSaber-1 encryption. $N must be a positive integer greater than one.

encrypt($message)

Encrypt a message. This uses the key stored in the current Crypt::CipherSaber object. It generates a 10-byte random IV (Initialization Vector) automatically, as defined in the RC4 specification. This returns a string containing the encrypted message.

Note that the encrypted message may contain unprintable characters, as it uses the extended ASCII character set (valid numbers 0 through 255).

decrypt($message)

Decrypt a message. For the curious, the first ten bytes of an encrypted message are the IV, so this must strip it off first. This returns a string containing the decrypted message.

The decrypted message may also contain unprintable characters, as the CipherSaber encryption scheme handles binary filesIf this is important to you, be sure to treat the results correctly.

crypt($iv, $message)

If you wish to generate the IV with a more cryptographically secure random string (at least compared to Perl's builtin rand() operator), you may do so separately, passing it to this method directly. The IV must be a ten-byte string consisting of characters from the extended ASCII set.

This is generally only useful for encryption, although you may extract the first ten characters of an encrypted message and pass them in yourself. You might as well call decrypt(), though. The more random the IV, the stronger the encryption tends to be. On some operating systems, you can read from /dev/random. Other approaches are the Math::TrulyRandom module, or compressing a file, removing the headers, and compressing it again.

fh_crypt(\*INPUT, \*OUTPUT, ($iv))

For the sake of efficiency, Crypt::CipherSaber can filehandles. It's not super brilliant, but it's relatively fast and sane. Pass in a reference to the input file handle and the output filehandle. If your platform needs to use binmode(), this is your responsibility. It is also your responsibility to close the files.

You may also pass in an optional third parameter, an IV. There are three possibilities here. If you pass no IV, fh_crypt() will pull the first ten bytes from the input filehandle and use that as an IV. This corresponds to decryption. If you pass in an IV of your own, it will use that when encrypting the file. If you pass in the value 1, it will generate a new, random IV for you. This corresponds to an encryption.

COPYRIGHT AND LICENSE ^

Copyright (C) 2000 - 2001, 2005 chromatic

This library is free software; you can use, modify, and redistribute it under the same terms as Perl 5.8.x itself.

AUTHOR ^

chromatic chromatic at wgz dot org

thanks to jlp for testing, moral support, and never fearing the icky details and to the fine folks at http://perlmonks.org/.

Additional thanks to Olivier Salaun and the Sympa project (http://www.sympa.org) for testing.

SEE ALSO ^

the CipherSaber home page at http://ciphersaber.gurus.com/

perl(1), rand().

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