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1. TPM-FAIL: TPM meets Timing and Lattice Attacks

   Moghimi, Daniel ; Sunar, Berk ; Eisenbarth, Thomas ; Heninger, Nadia ( January 2020 , Proceedings of the 29th USENIX Security Symposium)

   Trusted Platform Module (TPM) serves as a hardware based root of trust that protects cryptographic keys from privileged system and physical adversaries. In this work, we perform a black-box timing analysis of TPM 2.0 devices deployed on commodity computers. Our analysis reveals that some of these devices feature secret-dependent execution times during signature generation based on elliptic curves. In particular, we discovered timing leakage on an Intel firmware based TPM as well as a hardware TPM. We show how this information allows an attacker to apply lattice techniques to recover 256-bit private keys for ECDSA and ECSchnorr signatures. On Intel fTPM, our key recovery succeeds after about 1,300 observations and in less than two minutes. Similarly, we extract the private ECDSA key from a hardware TPM manufactured by STMicroelectronics, which is certified at Common Criteria (CC) EAL 4+, after fewer than 40,000 observations. We further highlight the impact of these vulnerabilities by demonstrating a remote attack against a StrongSwan IPsec VPN that uses a TPM to generate the digital signatures for authentication. In this attack, the remote client recovers the server’s private authentication key by timing only 45,000 authentication handshakes via a network connection. The vulnerabilities we have uncovered emphasizemore »the difficulty of correctly implementing known constant-time techniques, and show the importance of evolutionary testing and transparent evaluation of cryptographic implementations. Even certified devices that claim resistance against attacks require additional scrutiny by the community and industry, as we learn more about these attacks.« less
2. SIC ² : Securing Microcontroller Based IoT Devices with Low-cost Crypto Coprocessors

   https://doi.org/10.1109/ICPADS51040.2020.00057  

   Pearson, Bryan ; Zou, Cliff ; Zhang, Yue ; Ling, Zhen ; Fu, Xinwen ( December 2020 , 2020 IEEE 26th International Conference on Parallel and Distributed Systems (ICPADS))

   In this paper, we explore the use of microcontrollers (MCUs) and crypto coprocessors to secure IoT applications, and show how developers may implement a low-cost platform that provides protects private keys against software attacks. We first demonstrate the plausibility of format string attacks on the ESP32, a popular MCU from Espressif that uses the Harvard architecture. The format string attacks can be used to remotely steal private keys hard-coded in the firmware. We then present a framework termed SIC 2 (Securing IoT with Crypto Coprocessors), for secure key provisioning that protects end users' private keys from both software attacks and untrustworthy manufacturers. As a proof of concept, we pair the ESP32 with the low-cost ATECC608A cryptographic coprocessor by Microchip and connect to Amazon Web Services (AWS) and Amazon Elastic Container Service (EC2) using a hardware-protected private key, which provides the security features of TLS communication including authentication, encryption and integrity. We have developed a prototype and performed extensive experiments to show that the ATECC608A crypto chip may significantly reduce the TLS handshake time by as much as 82% with the remote server, and it may lower the total energy consumption of the system by up to 70%. Our results indicatemore »that securing IoT with crypto coprocessors is a practicable solution for low-cost MCU based IoT devices.« less
3. Biased Nonce Sense: Lattice Attacks Against Weak ECDSA Signatures in Cryptocurrencies

   https://doi.org/10.1007/978-3-030-32101-7_1  

   Breitner, Joachim ; Heninger, Nadia ( January 2019 , FC 2019: Financial Cryptography and Data Security)

   In this paper, we compute hundreds of Bitcoin private keys and dozens of Ethereum, Ripple, SSH, and HTTPS private keys by carrying out cryptanalytic attacks against digital signatures contained in public blockchains and Internet-wide scans. The ECDSA signature algorithm requires the generation of a per-message secret nonce. If this nonce is not generated uniformly at random, an attacker can potentially exploit this bias to compute the long-term signing key. We use a lattice-based algorithm for solving the hidden number problem to efficiently compute private ECDSA keys that were used with biased signature nonces due to multiple apparent implementation vulnerabilities.
4. SgxPectre: Stealing Intel Secrets from SGX Enclaves Via Speculative Execution

   https://doi.org/10.1109/EuroSP.2019.00020  

   Chen, Guoxing ; Chen, Sanchuan ; Xiao, Yuan ; Zhang, Yinqian ; Lin, Zhiqiang ; Lai, Ten H. ( June 2019 , IEEE European Symposium on Security and Privacy (EuroS&P))

   Speculative execution side-channel vulnerabilities in micro-architecture processors have raised concerns about the security of Intel SGX. To understand clearly the security impact of this vulnerability against SGX, this paper makes the following studies: First, to demonstrate the feasibility of the attacks, we present SgxPectre Attacks (the SGX-variants of Spectre attacks) that exploit speculative execution side-channel vulnerabilities to subvert the confidentiality of SGX enclaves. We show that when the branch prediction of the enclave code can be influenced by programs outside the enclave, the control flow of the enclave program can be temporarily altered to execute instructions that lead to observable cache-state changes. An adversary observing such changes can learn secrets inside the enclave memory or its internal registers, thus completely defeating the confidentiality guarantee offered by SGX. Second, to determine whether real-world enclave programs are impacted by the attacks, we develop techniques to automate the search of vulnerable code patterns in enclave binaries using symbolic execution. Our study suggests that nearly any enclave program could be vulnerable to SgxPectre Attacks since vulnerable code patterns are available in most SGX runtimes (e.g., Intel SGX SDK, Rust-SGX, and Graphene-SGX). Third, we apply SgxPectre Attacks to steal seal keys and attestation keys frommore »Intel signed quoting enclaves. The seal key can be used to decrypt sealed storage outside the enclaves and forge valid sealed data; the attestation key can be used to forge attestation signatures. For these reasons, SgxPectre Attacks practically defeat SGX's security protection. Finally, we evaluate Intel's existing countermeasures against SgxPectre Attacks and discusses the security implications.« less
5. CopyCat: Controlled Instruction-Level Attacks on Enclaves

   Moghimi, D. ; Van Bulck, J. ; Heninger, N. ; Piessens, F. ; Sunar, B. ( January 2020 , 29th USENIX Security Symposium (USENIX Security 20))

   The adversarial model presented by trusted execution environments (TEEs) has prompted researchers to investigate unusual attack vectors. One particularly powerful class of controlled-channel attacks abuses page-table modifications to reliably track enclave memory accesses at a page-level granularity. In contrast to noisy microarchitectural timing leakage, this line of deterministic controlled-channel attacks abuses indispensable architectural interfaces and hence cannot be mitigated by tweaking microarchitectural resources. We propose an innovative controlled-channel attack, named CopyCat, that deterministically counts the number of instructions executed within a single enclave code page. We show that combining the instruction counts harvested by CopyCat with traditional, coarse-grained page-level leakage allows the accurate reconstruction of enclave control flow at a maximal instruction-level granularity. CopyCat can identify intra-page and intra-cache line branch decisions that ultimately may only differ in a single instruction, underscoring that even extremely subtle control flow deviations can be deterministically leaked from secure enclaves. We demonstrate the improved resolution and practicality of CopyCat on Intel SGX in an extensive study of single-trace and deterministic attacks against cryptographic implementations, and give novel algorithmic attacks to perform single-trace key extraction that exploit subtle vulnerabilities in the latest versions of widely-used cryptographic libraries. Our findings highlight the importance of stricter verificationmore »of cryptographic implementations, especially in the context of TEEs.« less