Aristarkh A Zagorodnikov wrote:
> 
> >
> > On 24 Aug 2001 19:01:58 +0900, martin / zsdfherg.com wrote:
> > > Hi,
> > >
> > > This will likely turn out to be a dumb question, but is there any way to
> > > decrypt a string encrypted using String#crypt?
> > >

Use RC4 algorithm by Ron Rivest. In Ruby it's only four lines of code:

  s, j, k = (0..255).to_a, 0, (ARGV[0]*256)[0,256].unpack('C*')
  (0..255).each{|x| j = (j + s[x] + k[x]) % 256; s[x], s[j] = s[j], s[x] }
  i = j = 0; $stdin.each_byte{|b| i = (i + 1) % 256; j = (j + s[i]) % 256
  s[i], s[j] = s[j], s[i]; $stdout<<(b ^ s[(s[i] + s[j])%256]).chr }

This takes a string as parameter and encrypts/decrypts stdin to stdout.
Ha, Perl's version takes 3-4 lines, too.

RC4 is very simple to implementing but it is said to be insecure (whatever that means).

Regards,

  Michael

-- 
Michael Neumann
merlin.zwo InfoDesign GmbH
http://www.merlin-zwo.de