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Untargeted Attacks in (Password-Based) Cryptography

（基于密码的）密码学中的非针对性攻击

基本信息

批准号：
EP/V034065/1
负责人：
Pooya Farshim
金额：
$ 33.79万
依托单位：
Durham University
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2022
资助国家：
英国
起止时间：
2022 至无数据
项目状态：
未结题

来源：
https://gtr.ukri.org/projects?ref=EP%2FV034065%2F1
关键词：
Untargeted Attacks Password Based Cryptography

项目摘要

admin/123456; user/qwerty; root/vizxv; farshim/*********. Passwords permeate our lives: the security and privacy of many (perhaps all) of our on-line banking, commerce, and communication deeply rely on passwords. Yet they are one of the weakest links in securing systems. Storing username-passwords in plaintext, although convenient, seriously undermines security as evidenced by frequent leaks. Hashing passwords, i.e., applying a transformation that hides them, can reduce risks while still allowing for authentication. However, "123456" may well be a password chosen by someone, and then compromised. This proposal will address a current gap in our understanding of password-based cryptography in multi-instance environments where everyone is a target. We will investigate fundamental cryptographic techniques that are used to mitigate some of the risks associated in such environments. The novelty of our approach is that besides considering system-wide risks, we will consider preprocessing attacks which can speed up password-cracking by orders of magnitude. Our goal will be to show that the cryptanalytic effort needed to compromise users scales up well with the number of users targeted, and according to how "unguessable" system-wide passwords are. Formulating and studying measures of unguessability will be our starting point. These metrics will be developed with the view of usage in cryptographic contexts. For example, we will ask to what extent hashing of passwords preserves their unguessability. Crucially, we will incorporate appropriate modelling of preprocessing, so that amortised adversarial resources, such as the use of "rainbow tables," are accounted for. Alongside salting, which is a common practice to "decouple" security of users, we will consider deeper countermeasures. These include iteration, which slows down the rate of hashing, and modern memory-hard designs, which exploit uniformity of memory-access speeds across different platforms to thwart hardware-assisted attacks. In addition to unguessability, stronger notions of security that guarantee secure composition in a variety of contexts will be studied. Special attention will be paid to derive security bounds that are compatible with (real-world) parameters set according to best-known attacks. Alongside, we will also develop a solid understanding of the foundational cryptographic theory, as multi-instance security enjoys close links with amplification of hardness. The use of passwords is widespread in the security and ITC industries and their weakness is well recognised, especially in multi-user scenarios (such as IoT environments). This project will promote the creation of cryptographic standards for password hashing that are rigorously supported by security proofs. The final outcome will be an increased confidence in the resilience of our cyberspace.

管理员/123456；用户/qwerty；根/vizxv；法尔希姆/*********。密码渗透到我们的生活中：我们许多（也许是全部）在线银行、商业和通信的安全和隐私都深深依赖于密码。然而，它们是保护系统安全的最薄弱环节之一。以明文形式存储用户名密码虽然方便，但会严重破坏安全性，频繁的泄露就证明了这一点。对密码进行哈希处理，即应用隐藏密码的转换，可以降低风险，同时仍允许进行身份验证。然而，“123456”很可能是某人选择的密码，然后被泄露。该提案将解决目前我们在每个人都是目标的多实例环境中对基于密码的加密技术的理解上的差距。我们将研究用于减轻此类环境中相关风险的基本加密技术。我们方法的新颖之处在于，除了考虑系统范围的风险外，我们还将考虑预处理攻击，这可以将密码破解速度提高几个数量级。我们的目标是证明，危害用户所需的密码分析工作可以随着目标用户的数量以及系统范围密码的“不可猜测”程度而很好地扩展。制定和研究不可猜测性的度量将是我们的出发点。这些指标将根据加密环境中的使用情况来开发。例如，我们会询问密码散列在多大程度上保持其不可猜测性。至关重要的是，我们将结合适当的预处理建模，以便考虑摊销的对抗性资源，例如“彩虹表”的使用。除了加盐（这是“解耦”用户安全的常见做法）之外，我们还将考虑更深层次的对策。其中包括降低散列速度的迭代，以及利用不同平台上内存访问速度的一致性来阻止硬件辅助攻击的现代内存硬设计。除了不可猜测性之外，还将研究保证各种上下文中安全组合的更强的安全概念。将特别注意导出与根据最著名的攻击设置的（现实世界）参数兼容的安全边界。此外，我们还将对基础密码学理论有深入的了解，因为多实例安全性与硬度的放大有着密切的联系。密码的使用在安全和 ITC 行业中很广泛，并且它们的弱点是众所周知的，特别是在多用户场景（例如物联网环境）中。该项目将促进密码散列加密标准的创建，并得到安全证明的严格支持。最终结果将是增强人们对网络空间弹性的信心。