Whoops; and a question on information theory and encryption

[Clark Reynard]

Just noticed that my last note had been posted already;
sorry.

In addition, I'm wondering whether a plaintext/cyphertext pair is
considered to have a one-to-one isomorphism; in particular, in the
case where you have a plaintext/cyphertext pair but no knowledge of
the method of encryption, is there a one-to-one isomorphism?

In the case of a one-time pad, is there isomorphism, and if so, of
what sort?

Thank you.
----
Robert W. Clark             Just Say No! to the
rclark at nyx.cs.du.edu        Big Brother Chip