arXiv subjects

Arttu Paju

Publications and source records attributed to Arttu Paju.

4 recordsLinked to original sources

arXiv2026

External entropy supply for IoT devices employing a RISC-V Trusted Execution Environment

Entropy--a measure of randomness--is compulsory for the generation of secure cryptographic keys; however, Internet of Things (IoT) devices that are small or constrained often struggle to collect suf ficient entropy. In this article, we solve the entropy provisioning problem for a fleet of IoT devices that can generate a limited amount of entropy. We employ a Trusted Execution Environment (TEE) based on RISC-V to create an external entropy service for a fleet of IoT devices. A small measure of true entropy or pre-installed keys can establish initial secure communication. Once connected, devices can request cryptographically strong entropy from a TEE-backed server. RISC-V offers True Random Number Generators (TRNGs) and a TEE for devices to attest that they are receiving reliable entropy. In addition, this solution can be expanded by adding IoT devices with sensors that produce high-quality entropy as additional entropy sources for the RISC-V entropy provider. Our open-source implementation shows that building trusted entropy infrastructure for IoT is both feasible and effective on open RISC-V platforms.

cs.CR↗

arXiv2026

Measuring onion website discovery and Tor users' interests with honeypots

Tor enables anonymous web browsing and access to anonymous onion websites. Prior work has focused on crawling and content analysis rather than on what users actually try to access. Our honeypot approach measures engagement across onion-site categories, revealing behavioral interest rather than inferred popularity. In March--April 2025, we deployed honeypot onion websites and seeded neutral-looking links via three channels -- the Ahmia Tor search engine, Stronghold paste onion "paste" service, and pastebin.com -- to observe discovery and subsequent interaction events (CAPTCHA solves; registration/login attempts). We observe that, almost without exception, human users originate from Ahmia.fi; after removing the honeypot links from the Ahmia.fi search results, visits dropped to nearly zero and no users solved CAPTCHAs. The honeypot landing front pages represent different forums for cybercrime activities -- child sexual abuse, violence, malware, stolen goods, illegal firearms, illegal drugs, and forgery items -- and, as a baseline comparison, an unclear forum. Within that set, the CSAM-themed honeypot drew markedly higher engagement than the other honeypots. When identical sites were offered in multiple languages, interaction events occurred most often on the English-language versions.

cs.CR↗

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.

cs.CR↗

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.

cs.CR↗