this is the Ecrypto library, a group of files implementing strong
crypto in elisp.  it is made up of the following:

idea.el
  this file contains the code for the IDEA cipher.  it is reasonably
  secure, in terms of cleaning up intermediate computations.  the
  functions in it operate on 16-bit vectors.  CBC and a CBC-based
  package transform are provided.  XEmacs: this file was removed due
  to supposed patent problems.

md5.el, md5-old.el, sha1.el, sha1-old.el
  code for the MD5 and SHA-1 hash algorithms.  md5.el and sha1.el are
  the actual implementations, geared towards speed and data security
  (ie, wiping possibly sensitive data).  both files have to be
  compiled before being loaded.  md5-old.el and sha1-old.el are
  the original implementations, much more readable, less optimized,
  but slower and likely to leave secure data around for the GC to
  clean up.

ascii-armor.el
  provides routines for converting a vector of 16-bit numbers into its
  equivalent ascii-armor, and vice versa.  it could be easily extended
  to work for octet-streams, but hasn't, yet.

rc16.el
  code for Julian Assange's extension of RC4 to 16 bits.

rander.el
  this code attempts to provide cryptographically secure random
  numbers, but probably fails.  it draws together various sources of
  randomness from within emacs, including the microsecond timings of
  keypresses, though your emacs may not provide such timings.  this
  code should be considered somewhat untrustworthy.  it uses rc16.el
  for its core.

paranoid.el
  a slight modification to comint-read-noecho.  it leaves even less
  possibly sensitive data lying around for the GC to clean up. 

NOTES
----------------------------------------
IDEA is patented, but i believe that this software, which is GPL'd,
doesn't require any license fee or registration.  Diffie-Hellman was
patented, but that expired in 1997.  RC4 was a trade secret, it is no
longer, and so RC16 (which is based on RC4) is safe to use (with
credit to Julian Assange).

until this code has been extensively tested and examined by multiple
parties, i wouldn't trust it any more than a Cracker-Jack Secret
Decoder Ring.

enjoy.

ray jones
rjones@pobox.com