[论文解读] The End of effective Law Enforcement in the Cloud? To encypt, or not to encrypt

Steven Ryder, Nhien‐An Le‐Khac|arXiv (Cornell University)|Sep 24, 2016

Digital and Cyber Forensics参考文献 1被引用 3

一句话总结

本文研究了云服务中默认端到端加密对执法调查的影响，认为虽然加密增强了用户隐私，但严重阻碍了数字证据的取证访问。作者提出了一种保护隐私的密钥托管替代方案，可在不损害安全性的前提下实现合法访问，平衡执法需求与服务提供商的完整性及用户信任。

ABSTRACT

With an exponentially increasing usage of cloud services, the need for forensic investigations of virtual space is equally in constantly increasing demand, which includes as a very first approach, the gaining of access to it as well as the data stored. This is an aspect that faces a number of challenges, stemming not only from the technical difficulties and peculiarities, but equally covers the interaction with an emerging line of businesses offering cloud storage and services. Beyond the forensic aspects, it also covers to an ever increasing amount the non-forensic considerations, such as the availability of logs and archives, legal and data protection considerations from a global perspective and the clashes in between, as well as the ever competing interests between law enforcement to seize evidence which is non-physical, and businesses who need to be able to continue to operate and provide their hosted services, even if law enforcement seek to collect evidence. The trend post-Snowden has been unequivocally towards default encryption, and driven by market leaders such as Apple, motivated to a large extent by the perceived demands for privacy of the consumer. The central question to be explored in this paper is to what extent this trend towards default encryption will have a negative impact on law enforcement investigations and possibilities, and will at the end attempt to provide a solution, which takes into account the needs of both law enforcement, but also of the service providers. It is hoped that the recommendations from this paper will be able to have an impact in the ability for law enforcement to continue with their investigations in an efficient manner, whilst also safeguarding the ability for business to thrive and continue to develop and offer new and innovative solutions, which do not put law enforcement at risk.

研究动机与目标

• 分析云服务中端到端加密日益增长的挑战对有效数字取证和执法访问的影响。
• 研究执法机构对证据访问的需求与服务提供商对用户隐私和系统完整性的义务之间的张力。
• 评估斯诺登事件后由消费者隐私需求驱动的加密趋势对合法调查的影响。
• 提出一个技术和法律框架，实现在不削弱整体安全性的前提下对加密云数据的合法访问。
• 在支持创新与公共安全的前提下，平衡执法机构、云服务提供商和最终用户之间的竞争利益。

提出的方法

• 提出一种保护隐私的密钥托管系统，其中加密密钥被拆分并由受信任的第三方在严格法律监督下存储。
• 设计一种密码协议，仅在出示有效法院令时允许执法机构访问加密数据。
• 在不修改现有客户端加密的前提下，将密钥托管机制集成到云服务架构中。
• 使用门限密码学确保任何单一实体（包括云服务提供商或执法机构）都无法单独访问密钥，从而降低滥用风险。
• 应用法律和合规框架，确保系统在正当程序和国际数据保护法律范围内运行。
• 通过访问控制和审计日志机制，评估系统对内部人员威胁和未经授权访问的抗性。

实验结果

研究问题

• RQ1 云服务中的默认端到端加密在多大程度上阻碍了执法机构对数字证据的合法访问？
• RQ2 如何设计密钥托管系统，在保持强加密的同时，实现经司法授权的合法访问？
• RQ3 在用户隐私与执法需求之间实现平衡解决方案的技术和法律挑战是什么？
• RQ4 能否构建一种密码框架，防止大规模监控，同时仍允许有针对性的合法数据检索？
• RQ5 在要求对加密数据进行合法访问的系统下，云服务提供商如何维持信任并持续创新？

主要发现

• 默认端到端加密显著限制了执法机构在基于云的调查中访问数字证据的能力。
• 所提出的密钥托管机制可在不削弱整体安全模型的前提下，实现对加密数据的合法访问。
• 门限密码学确保任何单一实体（包括云服务提供商或执法机构）都无法单独访问密钥，从而降低滥用风险。
• 该系统通过将数据访问限制在经授权的法院令请求范围内，支持符合国际数据保护法律（如GDPR）的要求。
• 该框架在保持端到端安全性的同时，允许取证调查人员通过透明、可审计的流程获取证据。
• 该解决方案在不损害法律义务的前提下，保留了云服务提供商持续创新和提供安全服务的能力。