A new method is proposed to design short signature schemes based on difficulty of factorizing a composite number n = qr, where q and r are two large primes. Using the method new digital signature schemes (DSS) with the 320-bit and 240-bit signature size are developed. The characteristic feature of the 240-bit signature DSS is the use of "three-level" verification equation, for example, R = kgH mod n mod p, where k = Rg mod n mod p mod . The (k, g) signature corresponds to the H hash value and represents a pair of natural numbers having the size of 80 and 160 bits, respectively. The modulus is a prime number. The public key is the triple (, , p), where p = 2n + 1 is prime, is the q order element modulo p, is the order element modulo q. The private key is represented by the pair of two prime numbers (q, ).
Nikolay A. Moldovyan