🚀 go-pugleaf

I am looking for a piece of software that will test the "avalanche
effect" of any block cipher.  That is, it will somehow measure the
amount of intersymbol dependancies between the plaintext and the
ciphertext, and between the key and the ciphertext.  A good block
cipher will cause about half the ciphertext bits to change if only
one bit changes in the key, or if only one bit changes in the
plaintext.  A useful test program would systematically flip bits or
groups of bits in the key or the plaintext, and measure the
statistical properties of the bit changes in the ciphertext, going
through a large number of samples.  

It would save me some work if anyone has such a program handy, in
source form.  C would be nice.  If you have a lengthy answer that
would not be of interest to this newsgroup, you can reply via direct
email to me.  Thanks.

Philip Zimmermann   303/444-4541  prz@sage.cgd.ucar.edu