Blowfish has a 64-bit block size and a variable key length from 0 up to 448 bits It is a 16-round Feistel cipher and uses large key-dependent S-boxes . Blowfish has a 64-bit block size and a variable key length from 1 bit up to 448 bits . It is a 16-round Feistel cipher and uses large key-dependent S-boxes .