Ring signatures have been extensively researched for Cloud-assisted Electronic Medical Records (EMRs) sharing, aiming to address the challenge of “medical information silos” while safeguarding the privacy of patients’ personal information and the security of EMRs. However, most existing EMRs sharing systems that utilize ring signatures are vulnerable to quantum attacks, posing a severe challenge for the e-health scenario. To alleviate this issue, some studies have been conducted on lattice-based ring signatures. Nevertheless, there still exist two challenges. Firstly, current schemes fail to verify if multiple EMRs come from the same signer, undermining e-health reliability. Additionally, adversaries can exploit weaknesses in the network security of signers’ secret keys to forge signatures. In this paper, we propose an efficient lattice-based linkable ring signature (LLRS) for EMRs sharing to ensure patient privacy through anonymity, EMRs security through unforgeability, and checking the linkability for multiple signatures. We then present an enhancement scheme, called FS-LLRS, to additionally offer forward security, ensuring the security of previous ring signatures even if the current key has been compromised. To achieve this, we introduce a binary tree structure to divide time periods and leverage lattice basis algorithms for one-way secret key evolution, allowing users to update the secret keys periodically. Ultimately, we conduct a rigorous security analysis and compare our primitives with prior arts. In computational cost, the best performance of our LLRS and FS-LLRS schemes are just 0.17 and 0.34 times compared to others, respectively. Our LLRS scheme only incurs 0.08 times the communication overhead of others.

中文翻译：

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FS-LLRS：基于格子的可链接环签名，为云辅助电子病历提供前向安全性


环签名已被广泛研究用于云辅助电子病历 （EMR） 共享，旨在解决“医疗信息孤岛”的挑战，同时保护患者个人信息的隐私和 EMR 的安全。然而，大多数现有的利用环签名的 EMR 共享系统都容易受到量子攻击，这对电子健康场景构成了严峻的挑战。为了缓解这个问题，已经对基于晶格的环特征进行了一些研究。然而，仍然存在两个挑战。首先，目前的计划无法验证多个 EMR 是否来自同一个签名者，从而破坏了电子健康的可靠性。此外，攻击者可以利用签名者密钥的网络安全弱点来伪造签名。在本文中，我们提出了一种用于 EMR 共享的基于格的高效可链接环签名 （LLRS），以通过匿名性确保患者隐私，通过不可伪造性确保 EMR 安全性，并检查多个签名的可链接性。然后，我们提出了一种称为 FS-LLRS 的增强方案，以额外提供正向安全性，即使当前密钥已泄露，也能确保先前环签名的安全性。为此，我们引入了二叉树结构来划分时间段，并利用 lattice basis 算法进行单向密钥进化，允许用户定期更新密钥。最终，我们会进行严格的安全分析，并将我们的原语与以前的技术进行比较。在计算成本方面，我们的 LLRS 和 FS-LLRS 方案的最佳性能分别是其他方案的 0.17 倍和 0.34 倍。我们的 LLRS 方案产生的通信开销仅为其他方案的 0.08 倍。