To secure Vehicle-to-everything (V2X) communications, many Conditional Privacy-Preserving Authentication schemes (CPPA) use symmetric and asymmetric encryption during the authentication process. However, several existing schemes have some security limitations regarding VANET requirements. In many symmetric cryptography-based schemes, the participants are required to share the same keys which could compromise the security of the network in case the key of one participant is compromised, while many asymmetric cryptography-based schemes take much time during the authentication process, and don't address the denial-of-service attack. In this paper, we propose a certificateless scheme that does not require a certificate and prevents the escrow problem. Plus, it uses the elliptic curve cryptography and avoids bilinear pairing and Map-to-Hash functions. We call our scheme Hybrid Cryptography-Based Scheme with a Conditional Privacy-Preserving Authentication (HCBS-CPPA), as it uses both symmetric and asymmetric cryptography during the authentication process. Our scheme combines the strength of an asymmetric encryption that satisfies non-repudiation, and the strength of a symmetric encryption that allows to perform a lightweight authentication. In addition, we show that our scheme is resilient to memory-based Denial of Service (DOS) attack which occurs when an attacker floods the memory of a receiver with invalid messages. A security proof shows that HCBS-CPPA is secure in the random oracle. Regarding the simulation of our scheme, it turns out that HCBS-CPPA has the best performance when compared with several existing certificateless schemes. Additionally, it requires less execution time during the signing and verification process, as well as less communication overhead when compared to the existing schemes.

中文翻译：

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V2X 中基于混合密码学的方案，具有条件隐私保护身份验证和基于内存的 DOS 弹性


为了保护车对万物 (V2X) 通信的安全，许多条件隐私保护身份验证方案 (CPPA) 在身份验证过程中使用对称和非对称加密。然而，一些现有方案在 VANET 要求方面存在一些安全限制。在许多基于对称加密的方案中，参与者需要共享相同的密钥，如果一个参与者的密钥被泄露，这可能会危及网络的安全，而许多基于非对称加密的方案在身份验证过程中需要花费很多时间，并且不解决拒绝服务攻击。在本文中，我们提出了一种无需证书并防止托管问题的无证书方案。另外，它使用椭圆曲线加密技术并避免双线性配对和映射到哈希函数。我们将我们的方案称为具有条件隐私保护身份验证的基于混合加密的方案（HCBS-CPPA），因为它在身份验证过程中同时使用对称和非对称加密。我们的方案结合了满足不可否认性的非对称加密的强度和允许执行轻量级身份验证的对称加密的强度。此外，我们还表明，我们的方案能够抵御基于内存的拒绝服务（DOS）攻击，当攻击者用无效消息淹没接收者的内存时就会发生这种攻击。安全证明表明HCBS-CPPA在随机预言机中是安全的。关于我们的方案的模拟，结果表明，与现有的几种无证书方案相比，HCBS-CPPA 具有最佳性能。 此外，与现有方案相比，它在签名和验证过程中需要的执行时间更少，并且通信开销也更少。