arXiv subjects

Billy Bob Brumley

Publications and source records attributed to Billy Bob Brumley.

13 recordsLinked to original sources

arXiv2026

MIPSBLEED: Uncovering Microarchitectural Timing Leaks in Pervasive Embedded Processors

Despite their age, MIPS processors remain deeply embedded in routers, industrial controllers, and IoT systems, yet their security against modern side-channel attacks has received little attention. This paper exposes how Simultaneous Multithreading (SMT), a feature increasingly used to boost performance in these environments, creates powerful cross-core timing channels on MIPS-based platforms. We introduce MIPSBLEED, a systematic analysis and exploitation framework that uncovers leakage in three shared microarchitectural components: the L1 data cache, L1 instruction cache, and the execution engine. Through carefully crafted assembly-level probes and quantitative leakage assessment, we demonstrate practical, high-resolution timing attacks that operate without requiring privileged access. Our evaluation reveals significant information leakage across all three channels and culminates in a single trace key recovery attack on a real elliptic curve cryptographic toolkit. These results position MIPS as an overlooked yet critical target in the study of microarchitectural security and underscore the urgent need for lightweight isolation mechanisms in resource-constrained, SMT-enabled embedded systems.

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arXiv2026

SoK: The Constant Time Model

Constant time programming patterns is the primary defense against timing attacks on cryptographic implementations, yet what "constant time" means varies across academia and industry. This work systematizes constant time models and their evolution, identifies a recurring gap between what models protect and what specifications assume, and distills an offensive methodology for discovering timing vulnerabilities that originate outside the cryptographic primitive boundary. Applying this methodology, we locate a specification-level vulnerability related to private key loading, and confirm the leak in both OpenSSL and BoringSSL. Counterintuitively, BoringSSL's per-observation signal is several orders of magnitude stronger than OpenSSL's, despite an explicitly stricter threat model.

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arXiv2025

U Can Touch This! Microarchitectural Timing Attacks via Machine Clears

Microarchitectural timing attacks exploit subtle timing variations caused by hardware behaviors to leak sensitive information. In this paper, we introduce MCHammer, a novel side-channel technique that leverages machine clears induced by self-modifying code detection mechanisms. Unlike most traditional techniques, MCHammer does not require memory access or waiting periods, making it highly efficient. We compare MCHammer to the classical Flush+Reload technique, improving in terms of trace granularity, providing a powerful side-channel attack vector. Using MCHammer, we successfully recover keys from a deployed implementation of a cryptographic tool. Our findings highlight the practical implications of MCHammer and its potential impact on real-world systems.

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arXiv2024

Investigating child sexual abuse material availability, searches, and users on the anonymous Tor network for a public health intervention strategy

Tor is widely used for staying anonymous online and accessing onion websites; unfortunately, Tor is popular for distributing and viewing illicit child sexual abuse material (CSAM). From 2018 to 2023, we analyse 176,683 onion domains and find that one-fifth share CSAM. We find that CSAM is easily available using 21 out of the 26 most-used Tor search engines. We analyse 110,133,715 search sessions from the Ahmia.fi search engine and discover that 11.1% seek CSAM. When searching CSAM by age, 40.5% search for 11-year-olds and younger; 11.0% for 12-year-olds; 8.2% for 13-year-olds; 11.6% for 14-year-olds; 10.9% for 15-year-olds; and 12.7% for 16-year-olds. We demonstrate accurate filtering for search engines, introduce intervention, show a questionnaire for CSAM users, and analyse 11,470 responses. 65.3% of CSAM users first saw the material when they were children themselves, and half of the respondents first saw the material accidentally, demonstrating the availability of CSAM. 48.1% want to stop using CSAM. Some seek help through Tor, and self-help websites are popular. Our survey finds commonalities between CSAM use and addiction. Help-seeking correlates with increasing viewing duration and frequency, depression, anxiety, self-harming thoughts, guilt, and shame. Yet, 73.9% of help seekers have not been able to receive it.

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arXiv2023

SoK: A Systematic Review of TEE Usage for Developing Trusted Applications

Trusted Execution Environments (TEEs) are a feature of modern central processing units (CPUs) that aim to provide a high assurance, isolated environment in which to run workloads that demand both confidentiality and integrity. Hardware and software components in the CPU isolate workloads, commonly referred to as Trusted Applications (TAs), from the main operating system (OS). This article aims to analyse the TEE ecosystem, determine its usability, and suggest improvements where necessary to make adoption easier. To better understand TEE usage, we gathered academic and practical examples from a total of 223 references. We summarise the literature and provide a publication timeline, along with insights into the evolution of TEE research and deployment. We categorise TAs into major groups and analyse the tools available to developers. Lastly, we evaluate trusted container projects, test performance, and identify the requirements for migrating applications inside them.

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arXiv2023

Malware Finances and Operations: a Data-Driven Study of the Value Chain for Infections and Compromised Access

We investigate the criminal market dynamics of infostealer malware and publish three evidence datasets on malware infections and trade. We justify the value chain between illicit enterprises using the datasets, compare the prices and added value, and use the value chain to identify the most effective countermeasures. We begin by examining infostealer malware victim logs shared by actors on hacking forums, and extract victim information and mask sensitive data to protect privacy. We find access to these same victims for sale at Genesis Market. This technically sophisticated marketplace provides its own browser to access victim's online accounts. We collect a second dataset and discover that 91% of prices fall between 1--20 US dollars, with a median of 5 US dollars. Database Market sells access to compromised online accounts. We produce yet another dataset, finding 91% of prices fall between 1--30 US dollars, with a median of 7 US dollars.

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arXiv2021

OpenSSLNTRU: Faster post-quantum TLS key exchange

Google's CECPQ1 experiment in 2016 integrated a post-quantum key-exchange algorithm, newhope1024, into TLS 1.2. The Google-Cloudflare CECPQ2 experiment in 2019 integrated a more efficient key-exchange algorithm, ntruhrss701, into TLS 1.3. This paper revisits the choices made in CECPQ2, and shows how to achieve higher performance for post-quantum key exchange in TLS 1.3 using a higher-security algorithm, sntrup761. Previous work had indicated that ntruhrss701 key generation was much faster than sntrup761 key generation, but this paper makes sntrup761 key generation much faster by generating a batch of keys at once. Batch key generation is invisible at the TLS protocol layer, but raises software-engineering questions regarding the difficulty of integrating batch key exchange into existing TLS libraries and applications. This paper shows that careful choices of software layers make it easy to integrate fast post-quantum software, including batch key exchange, into TLS with minor changes to TLS libraries and no changes to applications. As a demonstration of feasibility, this paper reports successful integration of its fast sntrup761 library, via a lightly patched OpenSSL, into an unmodified web browser and an unmodified TLS terminator. This paper also reports TLS 1.3 handshake benchmarks, achieving more TLS 1.3 handshakes per second than any software included in OpenSSL.

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arXiv2021

Attestation Waves: Platform Trust via Remote Power Analysis

Attestation is a strong tool to verify the integrity of an untrusted system. However, in recent years, different attacks have appeared that are able to mislead the attestation process with treacherous practices as memory copy, proxy, and rootkit attacks, just to name a few. A successful attack leads to systems that are considered trusted by a verifier system, while the prover has bypassed the challenge. To mitigate these attacks against attestation methods and protocols, some proposals have considered the use of side-channel information that can be measured externally, as it is the case of electromagnetic (EM) emanation. Nonetheless, these methods require the physical proximity of an external setup to capture the EM radiation. In this paper, we present the possibility of performing attestation by using the side-channel information captured by a sensor or peripheral that lives in the same System-on-Chip (SoC) than the processor system (PS) which executes the operation that we aim to attest, by only sharing the Power Distribution Network (PDN). In our case, an analog-to-digital converter (ADC) that captures the voltage fluctuations at its input terminal while a certain operation is taking place is suitable to characterize itself and to distinguish it from other binaries. The resultant power traces are enough to clearly identify a given operation without the requirement of physical proximity.

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arXiv2021

HyperDegrade: From GHz to MHz Effective CPU Frequencies

Performance degradation techniques are an important complement to side-channel attacks. In this work, we propose HyperDegrade -- a combination of previous approaches and the use of simultaneous multithreading (SMT) architectures. In addition to the new technique, we investigate the root causes of performance degradation using cache eviction, discovering a previously unknown slowdown origin. The slowdown produced is significantly higher than previous approaches, which translates into an increased time granularity for Flush+Reload attacks. We evaluate HyperDegrade on different Intel microarchitectures, yielding significant slowdowns that achieve, in select microbenchmark cases, three orders of magnitude improvement over state-of-the-art. To evaluate the efficacy of performance degradation in side-channel amplification, we propose and evaluate leakage assessment metrics. The results evidence that HyperDegrade increases time granularity without a meaningful impact on trace quality. Additionally, we designed a fair experiment that compares three performance degradation strategies when coupled with Flush+Reload from an attacker perspective. We developed an attack on an unexploited vulnerability in OpenSSL in which HyperDegrade excels -- reducing by three times the number of required Flush+Reload traces to succeed. Regarding cryptography contributions, we revisit the recently proposed Raccoon attack on TLS-DH key exchanges, demonstrating its application to other protocols. Using HyperDegrade, we developed an end-to-end attack that shows how a Raccoon-like attack can succeed with real data, filling a missing gap from previous research.

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arXiv2021

Set It and Forget It! Turnkey ECC for Instant Integration

Historically, Elliptic Curve Cryptography (ECC) is an active field of applied cryptography where recent focus is on high speed, constant time, and formally verified implementations. While there are a handful of outliers where all these concepts join and land in real-world deployments, these are generally on a case-by-case basis: e.g. a library may feature such X25519 or P-256 code, but not for all curves. In this work, we propose and implement a methodology that fully automates the implementation, testing, and integration of ECC stacks with the above properties. We demonstrate the flexibility and applicability of our methodology by seamlessly integrating into three real-world projects: OpenSSL, Mozilla's NSS, and the GOST OpenSSL Engine, achieving roughly 9.5x, 4.5x, 13.3x, and 3.7x speedup on any given curve for key generation, key agreement, signing, and verifying, respectively. Furthermore, we showcase the efficacy of our testing methodology by uncovering flaws and vulnerabilities in OpenSSL, and a specification-level vulnerability in a Russian standard. Our work bridges the gap between significant applied cryptography research results and deployed software, fully automating the process.

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arXiv2021

Online Template Attacks: Revisited

An online template attack (OTA) is a powerful technique previously used to attack elliptic curve scalar multiplication algorithms. This attack has only been analyzed in the realm of power consumption and EM side channels, where the signals leak related to the value being processed. However, microarchitecture signals have no such feature, invalidating some assumptions from previous OTA works. In this paper, we revisit previous OTA descriptions, proposing a generic framework and evaluation metrics for any side-channel signal. Our analysis reveals OTA features not previously considered, increasing its application scenarios and requiring a fresh countermeasure analysis to prevent it. In this regard, we demonstrate that OTAs can work in the backward direction, allowing to mount an augmented projective coordinates attack with respect to the proposal by Naccache, Smart and Stern (Eurocrypt 2004). This demonstrates that randomizing the initial targeted algorithm state does not prevent the attack as believed in previous works. We analyze three libraries libgcrypt, mbedTLS, and wolfSSL using two microarchitecture side channels. For the libgcrypt case, we target its EdDSA implementation using Curve25519 twist curve. We obtain similar results for mbedTLS and wolfSSL with curve secp256r1. For each library, we execute extensive attack instances that are able to recover the complete scalar in all cases using a single trace. This work demonstrates that microarchitecture online template attacks are also very powerful in this scenario, recovering secret information without knowing a leakage model. This highlights the importance of developing secure-by-default implementations, instead of fix-on-demand ones.

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arXiv2020

Déjà Vu: Side-Channel Analysis of Mozilla's NSS

Recent work on Side Channel Analysis (SCA) targets old, well-known vulnerabilities, even previously exploited, reported, and patched in high-profile cryptography libraries. Nevertheless, researchers continue to find and exploit the same vulnerabilities in old and new products, highlighting a big issue among vendors: effectively tracking and fixing security vulnerabilities when disclosure is not done directly to them. In this work, we present another instance of this issue by performing the first library-wide SCA security evaluation of Mozilla's NSS security library. We use a combination of two independently-developed SCA security frameworks to identify and test security vulnerabilities. Our evaluation uncovers several new vulnerabilities in NSS affecting DSA, ECDSA, and RSA cryptosystems. We exploit said vulnerabilities and implement key recovery attacks using signals---extracted through different techniques such as timing, microarchitecture, and EM---and improved lattice methods.

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arXiv2020

Certified Side Channels

We demonstrate that the format in which private keys are persisted impacts Side Channel Analysis (SCA) security. Surveying several widely deployed software libraries, we investigate the formats they support, how they parse these keys, and what runtime decisions they make. We uncover a combination of weaknesses and vulnerabilities, in extreme cases inducing completely disjoint multi-precision arithmetic stacks deep within the cryptosystem level for keys that otherwise seem logically equivalent. Exploiting these vulnerabilities, we design and implement key recovery attacks utilizing signals ranging from electromagnetic (EM) emanations, to granular microarchitecture cache timings, to coarse traditional wall clock timings.

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