Deniable authentication protocols

Two deniable authentication schemes have been developed. One is based on th e intractability of the factoring problem, and the other is based on the in tractability of the discrete logarithm problem. The computation cost of the first scheme is about (t + 2)/2s. The second scheme requires about (2t + 3 )/4s of a previous scheme; s is the length of a message block and t is the cost of multiplication modN operations. It is shown that both protocols res erve all cryptographic characterisations of the previous scheme.