Overview of CA-1.0

  CA-1.0 is a cryptosystem designed to illustrate some of the principles underlying the use of cellular automata in cryptography. This section presents a brief overview of CA-1.0. Details are provided in succeeding sections.

• CA-1.0 is designed to be implemented in integrated circuits which are massively parallel and use mainly short-range connections between processors.
• CA-1.0 is a block-link cryptosystem. It uses 384-bit blocks and 320-bit links. Messages to be encrypted are encoded in the blocks, and the links are generated by a noise source within the encryption apparatus. Decryption recovers the blocks, and destroys the links.
• CA-1.0 uses a 1088-bit key. This key has two parts, a block key and a link key. The block key contains 1024 bits and the link key contains 64 bits.
• CA-1.0 is designed so that the link information is isolated from chosen-plaintext attack. It is not even possible to know the initial link information (link plaintext).
• CA-1.0 uses both reversible and irreversible CA rules. The irreversible rules are specified by the key, and the reversible rules are generated from the link.
• CA-1.0 uses two rounds of encryption/decryption. Each round is composed of a left- and a right-subround. Each subround, in turn, has a diffusion phase and a substitution phase.
• CA-1.0 uses irreversible toggle rules for the diffusion phases and reversible rules for the substitution phases.
• CA-1.0 is a low-aspect-ratio cryptosystem. It uses 32 iterations of an irreversible CA in each subround of encryption of 384-bit blocks, yielding an aspect ratio of .

• CA-1.0 features an embedded link-encryption system. Link encryption has the same format as block encryption, and some of the operations of the link-encryption system can be done in parallel with the operations of the block-encryption system.
• CA-1.0 allows for up to 100 blocks to be combined into a chain. Chain formation lowers the data-expansion rate. A chain of 100 blocks has a data-expansion rate of .

• CA-1.0 can functionally emulate DES in an appropriately secure environment, using 64-bit keys and (a multiple of) 64-bit blocks.

• Blocks, Links, and Chains
  • Chains.
• Rounds, Subrounds, and Phases