A Certificateless Public Key Cryptography (CL-PKC) aims to avoid the drawback of both traditional public key cryptography which requires a Public Key Infrastructure (PKI), and Identity-Based Public Key Cryptography (ID-PKC) which suffers from the inherent key escrow problem. In Vehicular Ad Hoc Network (VANET), a Certificateless Conditional Privacy Preserving Authentication (CCPPA) fulfills all known VANET security requirements in order to resolve challenges related to security and privacy. However, the existing certificateless schemes only achieve a trust level 2 according to the hierarchy defined by Girault. In case the partial private key is leaked, a malicious node can replace the public key since the public key is not bound to an identity. As a result, the trusted authority can only identify malicious nodes by using their pseudo identities. Al-Riyami and Paterson introduced a binding technique that allows to lift the trust level of a normal certificateless scheme to a trust level 3 by using a binding technique. This paper proposes new CCPPA schemes that use Al-Riyami and Paterson's technique, can achieve a stronger security and achieve a trust level 3. In case the partial private key is leaked, only the legitimate node can use the corresponding public key which has been certified by the trusted authority. As a result, the proposed CCPPA schemes address the vulnerability related to the public key replacement attack which is present in several CCPPA schemes. Our schemes also offer a tracing technique which consists of allowing the trusted authority to identify a malicious node using both its pseudo identity and public key. The proposed schemes use ECC cryptography and avoid Map-to-Hash function and bilinear pairing. Also, we called our schemes ECDSA-CCPPA and ECDSA*-CCPPA since they allow to respectively implement Elliptic Curve Digital Signature Algorithm (ECDSA) and the modified ECDSA* during authentication process in VANET. A security analysis is performed and proves that the ECDSA-CCPPA and ECDSA*-CCPPA schemes are secure in the random oracle. Actually, the ECDSA*-CCPPA scheme has an advantage over ECDSA-CCPPA in that it allows to perform a batch verification of signatures, where RSUs can support vehicles by collecting vehicle's signatures and verifying their messages in congested areas in order to reduce verification time. Additionally, a performance analysis is carried out to compare ECDSA*-CCPPA with several existing schemes. The simulation results show that ECDSA*-CCPPA outperforms the studied schemes with regard to the signature and verification process of one message. Moreover, it has the less overhead when compared to the studied certificateless schemes.

无证书公钥密码术 (CL-PKC) 旨在避免需要公钥基础设施 (PKI) 的传统公钥密码术和遭受固有密钥托管的基于身份的公钥密码术 (ID-PKC) 的缺点问题。在车载自组织网络 (VANET) 中，无证书条件隐私保护认证 (CCPPA) 满足所有已知的 VANET 安全要求，以解决与安全和隐私相关的挑战。然而，现有的无证书方案仅根据 Girault 定义的层次结构达到信任级别 2。如果部分私钥泄露，恶意节点可以替换公钥，因为公钥未绑定到身份。因此，受信任的权威机构只能通过使用他们的伪身份来识别恶意节点。Al-Riyami 和 Paterson 引入了一种绑定技术，该技术允许通过使用绑定技术将普通无证书方案的信任级别提升到信任级别 3。本文提出了新的 CCPPA 方案，使用 Al-Riyami 和 Paterson 技术，可以实现更强的安全性并达到 3 级信任。如果部分私钥泄露，只有合法节点可以使用相应的经过认证的公钥由受信任的权威机构。因此，提出的 CCPPA 方案解决了与几个 CCPPA 方案中存在的公钥替换攻击相关的漏洞。我们的方案还提供了一种跟踪技术，该技术包括允许受信任的机构使用其伪身份和公钥来识别恶意节点。所提出的方案使用 ECC 密码学并避免 Map-to-Hash 函数和双线性配对。此外，我们将我们的方案称为 ECDSA-CCPPA 和 ECDSA*-CCPPA，因为它们允许在 VANET 的身份验证过程中分别实现椭圆曲线数字签名算法 (ECDSA) 和修改后的 ECDSA*。进行安全分析，证明 ECDSA-CCPPA 和 ECDSA*-CCPPA 方案在随机预言机中是安全的。实际上，ECDSA*-CCPPA 方案比 ECDSA-CCPPA 方案的优势在于它允许执行批量签名验证，其中 RSU 可以通过收集车辆的签名并在拥挤区域验证其消息来支持车辆，以减少验证时间。此外，还进行了性能分析以将 ECDSA*-CCPPA 与几种现有方案进行比较。仿真结果表明，ECDSA*-CCPPA 在一条消息的签名和验证过程方面优于所研究的方案。此外，与研究的无证书方案相比，它的开销更少。