this concept is a fairly basic cryptographic primitive: http://en.wikipedia.org/wiki/Hash_chain

-bm

Quote from: mcdett on November 19, 2013, 02:49:24 PM

Did a little sleuthing today upon arriving to the office. I had remembered something from an old book I've had for more than 12 years. A book I used to help write some encryption classes in Java before Java offered them. I remembered that the author presented a payment system leveraging a protocol hashing and encryption. This wasn't my interest at the time, but somehow it stuck with me. Well I found the book again and did some reading (I've put this off too long).

"A really clever thing about this protocol is that the encryption key for each message depends on the previous message. Each message doubles as an authenticator for all previous messages. This means that someone can't replay an old message; the receiver could never decrypt it. I am impressed with this idea and expect that it will see wider use once it becomes widely known." [1]

I don't have the first edition of this book, so I don't know exactly when this was penned, but not after 1995.

[1] - Schneier, Bruce (1996). Applied Cryptography Second Edition : protocols, algorithms, and source code in C. John Wiley & Sons, Inc. p. 590