This paper will introduce two proposal algorithms (Snowfish 1) and the
(Snowfish 2) to improve the Sosemanuk stream cipher algorithm by benefiting from
the efficient properties of the Twofish block cipher and also use its key schedule, keydependent
Sbox to increase the security, randomness and try to avoid the guess and
determine attack of Sosemanuk. These two proposals use Twofish algorithm rather
than Serpent algorithm which was used in the Sosemanuk and also they use keydependent
Sbox rather than static Sbox. They are similar in the same key length (128
to 256 bit), IV length (128 bit), LFSR length, FSM functions and output
In this paper will make a comparison between Snowfish 1, Snowfish 2 and
Sosemanuk algorithms by using the tests of randomness, the structural tests and the
complexity of the algorithm. These tests give results that show the two proposed
algorithms have good results in increasing the security and randomness compared
with Sosemanuk algorithm.