[sci.crypt] Does encrypting a DES key with itself compromise the key?

lenoil@Apple.COM (Robert Lenoil) (03/10/88)

We wish to communicate a change in password between two trusted agents over
an untrusted medium in one packet.  The old password is known to both sides.
One scheme is to send the old and new passwords, both encrypted with the old
password.  Is this safe using DES as the encryption algorithm, i.e. can you
compute a string knowing the value of it encrypted with itself via DES?

Robert Lenoil
Apple Computer, Inc.