Abstract: On-line/off-line signcryption has the characteristics of low computation cost However, the existing on-line/off-line signcryption schemes arc based on certificate public key cryp tography and identity-based cryptography, which have the problems of certificate management or key escrow. Based on the merit of certificateless public key cryptography, an efficient certificateless on-line/off-line signcryption was proposed. The result shows that the new on-line/off-line signcryption scheme solves all the problems of certificate management and key escrow, and also satisfies all the required characteristics of signcryption. It is more efficient than the existed D)based on-line/off-line signcryption schemes and certificatcless on-line/off-line signcryption schemes.

Key words: On-line/off-line signcryption, Certificateless cryptography, Bilinear pairings, Random oracle model