Two varieties of finite automaton public key cryptosystem and digital signatures

DAFA - A Lightweight DES Augmented Finite Automaton Cryptosystem

“…Finite automata based public key cryptography termed FAPKC0 was introduced in [16] in 1985. Since then various public key cryptosystems based on finite automata have been proposed like FAPKC1, FAPKC2, FAPKC93, FAPKC3 and FAPKC4 [17,18,19].…”

“…The specifics of how this can be generated using the subkeys is as follows. For the first h 0 + k 0 component matrices, we use alternate subkeys K 1 , K 3 , K 5 and so on in a circular manner, rolling over to the beginning when we reach K 16 . Since we need only 64 bits in order to construct an 8X8 bit matrix, we use three permutation tables M-1, M-2 and M-3 (e.g., as shown in Tables 4, 5, 6) to derive 64 random bits from the 96-bit keys, using the similar operations as those in the PC-1 table (refer to…”

“…These are generated as in Step 2, except that they use the even set of subkeys K 2 , K 4 and so on in a circular manner, rolling over to the beginning when we reach K 16 . Also, as before, we use the permutation tables (e.g., M-1, M-2 and M-3) to derive the 64 random bits from the 96-bit keys.…”

A Novel Stream Cipher Based on Nondeterministic Finite Automata

“…Therefore, the cryptosystem based on nondeterministic finite automat cannot be attacked using reversibility. 6 …”

“…Firstly, the random number generator is independent from the key. Secondly, the weakly reversibility of automata does not affect the cryptosystem, so this system cannot be attacked with methods used for defeating FAPKC cryptosystems [5][6][7][8][9][10]. Thirdly, the key automaton is chosen randomly from a large set of automata with more than 256 states and more that 256 input signals, i.e., more than 256 (256!)…”