A Non-delegatable Identity-based Designated Verifier Signature Scheme without Bilinear Pairings

Abstract. Up to now, several non-delegatable identity-based (strong) designated verifier signature schemes using bilinear pairings are proposed. In these identity-based (strong) designated verifier signature schemes, bilinear pairings are employed either in signing and verifying steps or only in the verifying step. However, the computation cost of pairings at a security level equivalent to a 128-bit symmetric key of AES is approximately 20 times higher than that of exponentiation over an elliptic curve group. Hence, presenting a (strong) designated verifier signature scheme which is identity-based without pairings and supports non-delegatability as well is vital. In this study, a non-delegatable identity-based designated verifier signature scheme without bilinear pairings using two concatenated Schnorr signatures is proposed. Our construction not only is approximately 40 times more efficient compared to the existing non-delegatable identity-based (strong) designated verifier signature schemes due to the avoiding bilinear pairings but also it is provable secure in the random oracle