Abstract: A new certificateless signcyption scheme is given based on discrete logarithm and bilinear pairing.The new scheme satisfies the properties of confidentiality，verifiability，non-forgeability and so on.Besides，the trusted center KGC in this scheme can avoid being framed and its malicious behaviour can be discovered by the trace algorithm.So，the scheme realizes real non-repudiation and reaches trust level 3 defined by Girault by tracing KGC’s positive malicious attack.

Key words: certificateless public key cryptography, signcryption, bilinear pairing, discrete logarithm

摘要： 基于离散对数困难问题和双线性对映射知识，提出了一种新的无证书签密方案，该方案能够满足机密性、可验证性、不可伪造性。此外，方案可以避免KGC被陷害，而当出现争端时，方案中的追踪算法也能够对可信中心KGC的积极不诚实行为进行识别，从而实现了真正的不可否认性。由于方案可以识别KGC的积极恶意攻击，所以对可信中心KGC的信任可达到Girault定义的信任等级3。

关键词: 无证书公钥密码学, 签密, 双线性对, 离散对数问题