Symmetric encryption with multiple keys : techniques and applications

by Barlow, Lelia C.

Symmetric key block ciphers, such as AES, are well known and frequently used.

There are five confidentiality modes of operation that are currently recommended

for use with a symmetric key block cipher algorithm: Electronic Codebook (ECB),

Cipher Block Chaining (CBC), Cipher Feedback (CFB), Output Feedback (OFB),

and Counter (CTR).

This paper investigates extending the block cipher modes of operation using

multiple symmetric keys. Unlike traditional multiple-key encryption techniques,

each block of plaintext is encrypted using a single key. The key used to encrypt a

block is selected by the corresponding entry of a sequence. Each sequence entry

represents one of the independent keys in the set.

This paper also explores a variety of applications of this technique. Possible

applications include establishing a type of covert channel, customizing message

encryption at the block level, and expanding a string of pseudo-random numbers.

Simulations have been constructed to illustrate the concepts.