Content-Addressable Search Engines and DES-like Systems

Abstract

A very simple parallel architecture using a modified version of content-addressable memory (CAM) can be used to cheaply and efficiently encipher and decipher data with DES-like systems. This paper will describe how to implement DES on these modified content-addressable memories at speeds approaching some of the better specialized hardware. This implementation is often much more attractive for system designers because the CAM can be reprogrammed to encrypt the data with other DES-like systems such as Khufu or perform system tasks like data compression or graphics.The CAM memory architecture is also easily extendable to build a large scale engine for exhaustively searching the entire keyspace. This paper estimates that it will be possible to build a machine to test 255 keys of DES in one day for $30 million. This design is much less hypothetical than some of the others, in the literature because it is based upon hardware that will be available off-the-shelf in the late end of 1992. The architecture of this key search machine is much more attractive to an attacker because it is easily reprogrammable to handle modified DES-like algorithms such as the UNIX password system or Khufu.