TOWARD HIGHLY SECURE AND AUTONOMIC COMPUTING SYSTEMS: A HIERARCHICAL APPROACH

The overall objective of this research project is to develop novel architectural techniques as well as system software to achieve a highly secure and intrusion-tolerant computing system. Such system will be autonomous, self-adapting, introspective, with self-healing capability under the circumstances of improper operations, abnormal workloads, and malicious attacks. The scope of this research includes: (1) System-wide, unified introspection techniques for autonomic systems, (2) Secure information-flow microarchitecture, (3) Memory-centric security architecture, (4) Authentication control and its implication to security, (5) Digital right management, (5) Microarchitectural denial-of-service attacks on shared resources. During the period of the project, we developed several architectural techniques and system software for achieving a robust, secure, and reliable computing system toward our goal

Efficient Cache Attacks on AES, and Countermeasures

We describe several software side-channel attacks based on inter-process leakage through the state of the CPU's memory cache. This leakage reveals memory access patterns, which can be used for cryptanalysis of cryptographic primitives that employ data-dependent table lookups. The attacks allow an unprivileged process to attack other processes running in parallel on the same processor, despite partitioning methods such as memory protection, sandboxing, and virtualization. Some of our methods require only the ability to trigger services that perform encryption or MAC using the unknown key, such as encrypted disk partitions or secure network links. Moreover, we demonstrate an extremely strong type of attack, which requires knowledge of neither the specific plaintexts nor ciphertexts and works by merely monitoring the effect of the cryptographic process on the cache. We discuss in detail several attacks on AES and experimentally demonstrate their applicability to real systems, such as OpenSSL and Linux's dm-crypt encrypted partitions (in the latter case, the full key was recovered after just 800 writes to the partition, taking 65 milliseconds). Finally, we discuss a variety of countermeasures which can be used to mitigate such attacks

Design and evaluation of information flow signature for secure computation of applications

This thesis presents an architectural solution that provides secure and reliable execution of an application that computes critical data, in spite of potential hardware and software vulnerabilities. The technique does not require source code of or specifications about the malicious library function(s) called during execution of an application. The solution is based on the concept of Information Flow Signatures (IFS). The technique uses both a model-checker-based symbolic fault injection analysis tool called SymPLFIED to generate an IFS for an application or operating system, and runtime signature checking at the level of hardware to protect the integrity of critical data. The runtime checking is implemented in the IFS module. Reliable computation of data is ensured by the critical value re-computation (CVR) module. Prototype implementation of the signature checking and reliability module on a soft processor within an FPGA incurs no performance overhead and about 12% chip area overhead. The security module itself incurs about 7.5% chip area overhead. Performance evaluations indicate that the IFS module incurs as little as 3-4% overhead compared to 88-100% overhead when the runtime checking is implemented as a part of software. Preliminary testing indicates that the technique can provide 100% coverage for insider attacks that manifest as memory corruption and change the architectural state of the processor. Hence the IFS and CVR implementation offers a flexible, low-overhead, high-coverage method for ensuring reliable and secure computing

Hardware assisted control flow obfuscation for embedded processors

With more applications being deployed on embedded platforms, software protection becomes increasingly important. This problem is crucial on embedded systems like financial transaction terminals, pay-TV access-control decoders, where adversaries may easily gain full physical accesses to the systems and critical algorithms must be protected from being cracked. However, as this paper points out that protecting software with either encryption or obfuscation cannot completely preclude the control flow information from being leaked. Encryption has been widely studied and employed as a traditional approach for software protection, however, the control flow information is not 100 % hidden with solely encrypting the code. On the other hand, pure software-based obfuscation has been proved inefficient to protect software due to its lack of theoretical foundation and considerable performance overhead introduced by complicate

Evaluation Methodologies in Software Protection Research

Man-at-the-end (MATE) attackers have full control over the system on which the attacked software runs, and try to break the confidentiality or integrity of assets embedded in the software. Both companies and malware authors want to prevent such attacks. This has driven an arms race between attackers and defenders, resulting in a plethora of different protection and analysis methods. However, it remains difficult to measure the strength of protections because MATE attackers can reach their goals in many different ways and a universally accepted evaluation methodology does not exist. This survey systematically reviews the evaluation methodologies of papers on obfuscation, a major class of protections against MATE attacks. For 572 papers, we collected 113 aspects of their evaluation methodologies, ranging from sample set types and sizes, over sample treatment, to performed measurements. We provide detailed insights into how the academic state of the art evaluates both the protections and analyses thereon. In summary, there is a clear need for better evaluation methodologies. We identify nine challenges for software protection evaluations, which represent threats to the validity, reproducibility, and interpretation of research results in the context of MATE attacks

ABSTRACT + Hardware Assisted Control Flow Obfuscation for Embedded Processors

With more applications being deployed on embedded platforms, software protection becomes increasingly important. This problem is crucial on embedded systems like financial transaction terminals, pay-TV access-control decoders, where adversaries may easily gain full physical accesses to the systems and critical algorithms must be protected from being cracked. However, as this paper points out that protecting software with either encryption or obfuscation cannot completely preclude the control flow information from being leaked. Encryption has been widely studied and employed as a traditional approach for software protection, however, the control flow information is not 100 % hidden with solely encrypting the code. On the other hand, pure software-based obfuscation has been proved inefficient to protect software due to its lack of theoretical foundation and considerable performance overhead introduced by complicated transformations. Moreover, even though obfuscation can prevent static reverse engineering, attacker can still successfully bypass the obfuscation by monitoring the dynamic program execution. To address all of these shortcomings, this paper presents a hardware assisted obfuscation technique that is capable of obfuscating the control flow information dynamically. Dynamic obfuscation changes memory access sequence on-the-fly and conceals recurrent instruction access sequences from being identified. Our scheme makes it provably difficult for the attacker to extract any useful information. Our results show that a highlevel security protection is possible with only minor performance penalty. Finally, we show that our scheme can be implemented on embedded systems with very little hardware overhead