mecacipher

A chaos-based, metamorphic block cipher based on second-order cellular automata (MECA).

• Fully templated to accomodate block-sizes of up to 256 bits (64/128/256 bits have been tested)
• Key size of up to 255 bytes
  • Metamorphically evolved key schedule using globally chaotic (class 4) rules of elementary CA (irreversible)
• Metamorphic engine to select second-order rules to evolve based on incoming data
• Configurable rounds for added security

Key Schedule

The key schedule has been adapted from RC6's algorithm, you will find it using the same magic constants with 4 less words if the number of desired keys is greater than the key generating key length.

Magic constants

• Let P = the binary expansion of Euler's number - 2

• Let Q = the binary expansion of the golden ratio - 1

The schedule is initialized with the first element set to P. The rest of the schedule is initialized additively using the previous key + Q. For 3 * max(key length, num_keys) iterations, the keys XORed with the key-generating-key and metamorphically evolved using irreversible class 4 elementary cellular automata rules (54, 110, and 137).

Rule 54

Rule 110

Rule 137

Metamorphic Engine

The metamorphic engine selects rules for the second-order automata given the state of the CA during a given encryption/decryption round. These rules have been selected based on their sensitivity to initial conditions and differential cryptanalysis (see Cryptographic Properties of Second-Order Memory Elementary Cellular Automata)

Rule 75

Rule 86

Rule 89

Rule 149

Rule 166

Rule 173

Rule 229

Output

Configured for 15 rounds

64-bit block size

PLAINTEXT: 1337 1337 1337 1337
KEY      : 4d79 2063 7269 6d65 2069 7320 7468 6174 206f 6620 6375 7269 6f73 6974 7900
ENCRYPTED: ee1c fa14 68e1 51c8
DECRYPTED: 1337 1337 1337 1337
ENC TIME : 37 microseconds
DEC TIME : 33 microseconds

128-bit block size

PLAINTEXT: 00001337 00001337 00001337 00001337
KEY      : 4d792063 72696d65 20697320 74686174 206f6620 63757269 6f736974 79000000
ENCRYPTED: d93041ec e3fa5b94 01a2df58 71ca05ab
DECRYPTED: 00001337 00001337 00001337 00001337
ENC TIME : 47 microseconds
DEC TIME : 35 microseconds

256-bit block size

PLAINTEXT: 0000000000001337 0000000000001337 0000000000001337 0000000000001337
KEY      : 4d79206372696d65 2069732074686174 206f662063757269 6f73697479000000
ENCRYPTED: e72d26f7318d3da2 0ec874868d14ac9b 7d91e0e34ee12d46 0fd1e08f367ad342
DECRYPTED: 0000000000001337 0000000000001337 0000000000001337 0000000000001337
ENC TIME : 78 microseconds
DEC TIME : 61 microseconds

Future plans

• Metamorphic engine for key-generating-key combination with key schedule (xor, add, subtract, invert, etc)

References

• Second-order cellular automaton
• Cryptographic Properties of Second-Order Memory Elementary Cellular Automata
• The Stone Cipher-192 (SC-192): A Metamorphic Cipher