Recovering OpenSSL ECDSA Nonces Using the FLUSH+RELOAD Cache Side-channel Attack

We illustrate a vulnerability introduced to elliptic curve cryptographic protocols when implemented using a function of the OpenSSL cryptographic library. For the given implementation using an elliptic curve E over a binary field with a point G \in E, our attack recovers the majority of the bits of a scalar k when kG is computed using the OpenSSL implementation of the Montgomery ladder. For the Elliptic Curve Digital Signature Algorithm (ECDSA) the scalar k is intended to remain secret. Our attack recovers the scalar k and thus the secret key of the signer and would therefore allow unlimited forgeries. This is possible from snooping on only one signing process and requires computation of less than one second on a quad core desktop when the scalar k (and secret key) is around 571 bits

Physical Fault Injection and Side-Channel Attacks on Mobile Devices:A Comprehensive Analysis

Today's mobile devices contain densely packaged system-on-chips (SoCs) with multi-core, high-frequency CPUs and complex pipelines. In parallel, sophisticated SoC-assisted security mechanisms have become commonplace for protecting device data, such as trusted execution environments, full-disk and file-based encryption. Both advancements have dramatically complicated the use of conventional physical attacks, requiring the development of specialised attacks. In this survey, we consolidate recent developments in physical fault injections and side-channel attacks on modern mobile devices. In total, we comprehensively survey over 50 fault injection and side-channel attack papers published between 2009-2021. We evaluate the prevailing methods, compare existing attacks using a common set of criteria, identify several challenges and shortcomings, and suggest future directions of research

Side-Channel Analysis and Cryptography Engineering : Getting OpenSSL Closer to Constant-Time

As side-channel attacks reached general purpose PCs and started to be more practical for attackers to exploit, OpenSSL adopted in 2005 a flagging mechanism to protect against SCA. The opt-in mechanism allows to flag secret values, such as keys, with the BN_FLG_CONSTTIME flag. Whenever a flag is checked and detected, the library changes its execution flow to SCA-secure functions that are slower but safer, protecting these secret values from being leaked. This mechanism favors performance over security, it is error-prone, and is obscure for most library developers, increasing the potential for side-channel vulnerabilities. This dissertation presents an extensive side-channel analysis of OpenSSL and criticizes its fragile flagging mechanism. This analysis reveals several flaws affecting the library resulting in multiple side-channel attacks, improved cache-timing attack techniques, and a new side channel vector. The first part of this dissertation introduces the main topic and the necessary related work, including the microarchitecture, the cache hierarchy, and attack techniques; then it presents a brief troubled history of side-channel attacks and defenses in OpenSSL, setting the stage for the related publications. This dissertation includes seven original publications contributing to the area of side-channel analysis, microarchitecture timing attacks, and applied cryptography. From an SCA perspective, the results identify several vulnerabilities and flaws enabling protocol-level attacks on RSA, DSA, and ECDSA, in addition to full SCA of the SM2 cryptosystem. With respect to microarchitecture timing attacks, the dissertation presents a new side-channel vector due to port contention in the CPU execution units. And finally, on the applied cryptography front, OpenSSL now enjoys a revamped code base securing several cryptosystems against SCA, favoring a secure-by-default protection against side-channel attacks, instead of the insecure opt-in flagging mechanism provided by the fragile BN_FLG_CONSTTIME flag

Trusted Execution Development: Designing a Secure, High-Performance Remote Attestation Protocol

Intel Software Guard Extensions (SGX) are a Trusted Execution Environment (TEE) technology that allow programs to protect execution process and data from other processes on the platform. We propose a method to combine SGX attestation with Transport Layer Security (TLS). Doing so will combine guarantees about the program, runtime environment, and machine identity into a normal TLS handshake. We implemented a basic server using SGX/TLS and provide performance details and lessons learned during development