Crypt::CVS - Substitution cipher for CVS passwords


    use Crypt::CVS qw(:all);

    # AE00uy
    my $scrambled = scramble "foobar";
    # foobar
    my $descrambled = descramble $scrambled;


The CVS protocol uses a substitution cipher for passwords going over the wire. From src/scramble.c in GNU CVS's source distribution:

    Trivially encode strings to protect them from innocent eyes (i.e.,
    inadvertent password compromises, like a network administrator
    who's watching packets for legitimate reasons and accidentally sees
    the password protocol go by.

About the encoding:

    Map characters to each other randomly and symmetrically, A <--> B.

    We divide the ASCII character set into 3 domains: control chars (0
    thru 31), printing chars (32 through 126), and "meta"-chars (127
    through 255).  The control chars map _to_ themselves, the printing
    chars map _among_ themselves, and the meta chars map _among_
    themselves.  Why is this thus?

    No character in any of these domains maps to a character in another
    domain, because I'm not sure what characters are valid in
    passwords, or what tools people are likely to use to cut and paste
    them.  It seems prudent not to introduce control or meta chars,
    unless the user introduced them first.  And having the control
    chars all map to themselves insures that newline and
    carriage-return are safely handled.



Takes plaintext and returns a scrambled version of it. The first byte of the scrambled string is a single letter indicating the scrambling method. This has always been "A", it's very unlikely that there'll ever be another scrambling method.


Takes a scrambled string and returns an unscrambled version. Dies if the first letter isn't "A".


The functions "scramble" and "descramble" can be optionally exported. use Crypt::CVS ':all' exports both of them.


Ævar Arnfjörð Bjarmason <>


Copyright 2007-2010 Ævar Arnfjörð Bjarmason.

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.