Secure Information Flow by Model Checking Pushdown System

利用安全异构时间源检测GNSS异常行为

Detecting GNSS misbehavior leveraging secure heterogeneous time sources

针对民用GNSS脆弱性威胁关键系统的问题，提出结合安全远程网络授时源与本地精密振荡器的多层防御机制，无需改动现有接收机即可检测微小时间偏移的GNSS攻击，兼容性强易部署。

Checking Interaction-Based Declassification Policies for Android Using Symbolic Execution

Mobile apps can access a wide variety of secure information, such as contacts and location. However, current mobile platforms include only coarse access control mechanisms to protect such data. In this paper, we introduce interaction-based declassification policies, in which the user's interactions with the app constrain the release of sensitive information. Our policies are defined extensionally, so as to be independent of the app's implementation, based on sequences of security-relevant events that occur in app runs. Policies use LTL formulae to precisely specify which secret inputs, read at…

Information Flow Control-by-Construction for an Object-Oriented Language Using Type Modifiers

In security-critical software applications, confidential information must be prevented from leaking to unauthorized sinks. Static analysis techniques are widespread to enforce a secure information flow by checking a program after construction. A drawback of these systems is that incomplete programs during construction cannot be checked properly. The user is not guided to a secure program by most systems. We introduce IFbCOO, an approach that guides users incrementally to a secure implementation by using refinement rules. In each refinement step, confidentiality or integrity (or both) is guaran…

A Permission-Dependent Type System for Secure Information Flow Analysis

We introduce a novel type system for enforcing secure information flow in an imperative language. Our work is motivated by the problem of statically checking potential information leakage in Android applications. To this end, we design a lightweight type system featuring Android permission model, where the permissions are statically assigned to applications and are used to enforce access control in the applications. We take inspiration from a type system by Banerjee and Naumann (BN) to allow security types to be dependent on the permissions of the applications. A novel feature of our type syst…

Parametric Timed Model Checking for Guaranteeing Timed Opacity

Information leakage can have dramatic consequences on systems security. Among harmful information leaks, the timing information leakage is the ability for an attacker to deduce internal information depending on the system execution time. We address the following problem: given a timed system, synthesize the execution times for which one cannot deduce whether the system performed some secret behavior. We solve this problem in the setting of timed automata (TAs). We first provide a general solution, and then extend the problem to parametric TAs, by synthesizing internal timings making the TA sec…

针对推测执行信息泄露的自动与增量修复

Automatic and Incremental Repair for Speculative Information Leaks

提出首个基于模型检测的框架CureSpec，通过形式化攻击者模型自动检测并修复程序在侧信道和推测执行下的信息泄露，插入缓解措施确保代码可证明安全，并提供可独立检查的安全证书。

An Automated Analysis of the Security of Quantum Key Distribution

This paper discusses the use of computer-aided verification as a practical means for analysing quantum information systems; specifically, the BB84 protocol for quantum key distribution is examined using this method. This protocol has been shown to be unconditionally secure against all attacks in an information-theoretic setting, but the relevant security proof requires a thorough understanding of the formalism of quantum mechanics and is not easily adaptable to practical scenarios. Our approach is based on probabilistic model-checking; we have used the PRISM model-checker to show that, as the …

Quantitative Information Flow - Verification Hardness and Possibilities

Researchers have proposed formal definitions of quantitative information flow based on information theoretic notions such as the Shannon entropy, the min entropy, the guessing entropy, and channel capacity. This paper investigates the hardness and possibilities of precisely checking and inferring quantitative information flow according to such definitions. We prove that, even for just comparing two programs on which has the larger flow, none of the definitions is a k-safety property for any k, and therefore is not amenable to the self-composition technique that has been successfully applied to…

Security policies for distributed systems

A security policy specifies a security property as the maximal information flow. A distributed system composed of interacting processes implicitly defines an intransitive security policy by repudiating direct information flow between processes that do not exchange messages directly. We show that implicitly defined security policies in distributed systems are enforced, provided that processes run in separation, and possible process communication on a technical platform is restricted to specified message paths of the system. Furthermore, we propose to further restrict the allowable information f…

从孤立指令到交互式鼓励！基于自然语言提示的大语言模型安全代码生成

From Solitary Directives to Interactive Encouragement! LLM Secure Code Generation by Natural Language Prompting

本文提出SecCode框架，通过仅使用自然语言提示的交互式鼓励提示（EP）技术，经多阶段迭代实现代码生成、漏洞检测修复与安全精化，在多个大模型和基准上显著提升安全代码生成效果。

Quantifying Information Leak Vulnerabilities

Leakage of confidential information represents a serious security risk. Despite a number of novel, theoretical advances, it has been unclear if and how quantitative approaches to measuring leakage of confidential information could be applied to substantial, real-world programs. This is mostly due to the high complexity of computing precise leakage quantities. In this paper, we introduce a technique which makes it possible to decide if a program conforms to a quantitative policy which scales to large state-spaces with the help of bounded model checking. Our technique is applied to a number of o…

用于半自动化检查研究产出的多语言工具包

A multi-language toolkit for the semi-automated checking of research outputs

本文介绍开源多语言工具包SACRO，在安全数据环境中半自动化检查研究产出的隐私披露，通过轻量级Python包辅助人工检查员应用统计披露控制技术，提升审核效率与可审计性。