arXiv subjects

Alan T. Sherman

Publications and source records attributed to Alan T. Sherman.

14 recordsLinked to original sources

arXiv2026

Verifying Provenance of Digital Media: Why the C2PA Specifications Fall Short

The rapid rise of generative AI has made it easy to create convincing fake media at scale. In response, an industrial coalition has developed the Coalition for Content Provenance and Authenticity (C2PA), a system intended to provide verifiable provenance for digital content. Our research team conducted the first comprehensive, independent security analysis of C2PA. Our study includes the first formal-methods analysis of C2PA's core protocols. We find that the current C2PA specifications fail to achieve their claimed security goals. Furthermore, they also fail to achieve key additional goals, which all such provenance systems require for trustworthy deployment. As a result, C2PA may mislead users, platforms, and policymakers if relied upon prematurely. C2PA is a promising idea, but it should not yet be relied upon for high-stakes uses such as financial disclosures, journalism, or legal evidence.

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arXiv2025

Analysis of the Security Design, Engineering, and Implementation of the SecureDNA System

We analyze security aspects of the SecureDNA system regarding its system design, engineering, and implementation. This system enables DNA synthesizers to screen order requests against a database of hazards. By applying novel cryptography, the system aims to keep order requests and the database of hazards secret. Discerning the detailed operation of the system in part from source code (Version 1.0.8), our analysis examines key management, certificate infrastructure, authentication, and rate-limiting mechanisms. We also perform the first formal-methods analysis of the mutual authentication, basic request, and exemption-handling protocols. Without breaking the cryptography, our main finding is that SecureDNA's custom mutual authentication protocol SCEP achieves only one-way authentication: the hazards database and keyservers never learn with whom they communicate. This structural weakness violates the principle of defense in depth and enables an adversary to circumvent rate limits that protect the secrecy of the hazards database, if the synthesizer connects with a malicious or corrupted keyserver or hashed database. We point out an additional structural weakness that also violates the principle of defense in depth: inadequate cryptographic bindings prevent the system from detecting if responses, within a TLS channel, from the hazards database were modified. Consequently, if a synthesizer were to reconnect with the database over the same TLS session, an adversary could replay and swap responses from the database without breaking TLS. Although the SecureDNA implementation does not allow such reconnections, it would be stronger security engineering to avoid the underlying structural weakness. We identify these vulnerabilities and suggest and verify mitigations, including adding strong bindings. Software Version 1.1.0 fixes SCEP with our proposed SCEP+ protocol.

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arXiv2025

Cryptographic Binding Should Not Be Optional: A Formal-Methods Analysis of FIDO UAF Channel Binding

As a case study in cryptographic binding, we present a formal-methods analysis of the cryptographic channel binding mechanisms in the Fast IDentity Online (FIDO) Universal Authentication Framework (UAF) authentication protocol, which seeks to reduce the use of traditional passwords in favor of authentication devices. First, we show that UAF's channel bindings fail to mitigate protocol interaction by a Dolev-Yao adversary, enabling the adversary to transfer the server's authentication challenge to alternate sessions of the protocol. As a result, in some contexts, the adversary can masquerade as a client and establish an authenticated session with a server (e.g., possibly a bank server). Second, we implement a proof-of-concept man-in-the-middle attack against eBay's open source FIDO UAF implementation. Third, we propose and formally verify improvements to UAF. The weakness we analyze is similar to the vulnerability discovered in the Needham-Schroeder protocol over 25 years ago. That this vulnerability appears in the FIDO UAF standard highlights the strong need for protocol designers to bind messages properly and to analyze their designs with formal-methods tools. To our knowledge, we are first to carry out a formal-methods analysis of channel binding in UAF and first to exhibit details of an attack on UAF that exploits the weaknesses of UAF's channel binding. Our case study illustrates the importance of cryptographically binding context to protocol messages to prevent an adversary from misusing messages out of context.

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arXiv2021

AOT: Anonymization by Oblivious Transfer

We introduce AOT, an anonymous communication system based on mix network architecture that uses oblivious transfer (OT) to deliver messages. Using OT to deliver messages helps AOT resist blending ($n-1$) attacks and helps AOT preserve receiver anonymity, even if a covert adversary controls all nodes in AOT. AOT comprises three levels of nodes, where nodes at each level perform a different function and can scale horizontally. The sender encrypts their payload and a tag, derived from a secret shared between the sender and receiver, with the public key of a Level-2 node and sends them to a Level-1 node. On a public bulletin board, Level-3 nodes publish tags associated with messages ready to be retrieved. Each receiver checks the bulletin board, identifies tags, and receives the associated messages using OT. A receiver can receive their messages even if the receiver is offline when messages are ready. Through what we call a "handshake" process, communicants can use the AOT protocol to establish shared secrets anonymously. Users play an active role in contributing to the unlinkability of messages: periodically, users initiate requests to AOT to receive dummy messages, such that an adversary cannot distinguish real and dummy requests.

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arXiv2021

Boardroom Voting: Verifiable Voting with Ballot Privacy Using Low-Tech Cryptography in a Single Room

A boardroom election is an election that takes place in a single room -- the boardroom -- in which all voters can see and hear each other. We present an initial exploration of boardroom elections with ballot privacy and voter verifiability that use only "low-tech cryptography" without using computers to mark or collect ballots. Specifically, we define the problem, introduce several building blocks, and propose a new protocol that combines these blocks in novel ways. Our new building blocks include "foldable ballots" that can be rotated to hide the alignment of ballot choices with voting marks, and "visual secrets" that are easy to remember and use but hard to describe. Although closely seated participants in a boardroom election have limited privacy, the protocol ensures that no one can determine how others voted. Moreover, each voter can verify that their ballot was correctly cast, collected, and counted, without being able to prove how they voted, providing assurance against undue influence. Low-tech cryptography is useful in situations where constituents do not trust computer technology, and it avoids the complex auditing requirements of end-to-end cryptographic voting systems such as Prêt-à-Voter. This paper's building blocks and protocol are meant to be a proof of concept that might be tested for usability and improved.

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arXiv2020

BVOT: Self-Tallying Boardroom Voting with Oblivious Transfer

A boardroom election is an election with a small number of voters carried out with public communications. We present BVOT, a self-tallying boardroom voting protocol with ballot secrecy, fairness (no tally information is available before the polls close), and dispute-freeness (voters can observe that all voters correctly followed the protocol). BVOT works by using a multiparty threshold homomorphic encryption system in which each candidate is associated with a masked unique prime. Each voter engages in an oblivious transfer with an untrusted distributor: the voter selects the index of a prime associated with a candidate and receives the selected prime in masked form. The voter then casts their vote by encrypting their masked prime and broadcasting it to everyone. The distributor does not learn the voter's choice, and no one learns the mapping between primes and candidates until the audit phase. By hiding the mapping between primes and candidates, BVOT provides voters with insufficient information to carry out effective cheating. The threshold feature prevents anyone from computing any partial tally---until everyone has voted. Multiplying all votes, their decryption shares, and the unmasking factor yields a product of the primes each raised to the number of votes received. In contrast to some existing boardroom voting protocols, BVOT does not rely on any zero-knowledge proof; instead, it uses oblivious transfer to assure ballot secrecy and correct vote casting. Also, BVOT can handle multiple candidates in one election. BVOT prevents cheating by hiding crucial information: an attempt to increase the tally of one candidate might increase the tally of another candidate. After all votes are cast, any party can tally the votes.

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arXiv2020

Experiences and Lessons Learned Creating and Validating Concept Inventories for Cybersecurity

We reflect on our ongoing journey in the educational Cybersecurity Assessment Tools (CATS) Project to create two concept inventories for cybersecurity. We identify key steps in this journey and important questions we faced. We explain the decisions we made and discuss the consequences of those decisions, highlighting what worked well and what might have gone better. The CATS Project is creating and validating two concept inventories---conceptual tests of understanding---that can be used to measure the effectiveness of various approaches to teaching and learning cybersecurity. The Cybersecurity Concept Inventory (CCI) is for students who have recently completed any first course in cybersecurity; the Cybersecurity Curriculum Assessment (CCA) is for students who have recently completed an undergraduate major or track in cybersecurity. Each assessment tool comprises 25 multiple-choice questions (MCQs) of various difficulties that target the same five core concepts, but the CCA assumes greater technical background. Key steps include defining project scope, identifying the core concepts, uncovering student misconceptions, creating scenarios, drafting question stems, developing distractor answer choices, generating educational materials, performing expert reviews, recruiting student subjects, organizing workshops, building community acceptance, forming a team and nurturing collaboration, adopting tools, and obtaining and using funding. Creating effective MCQs is difficult and time-consuming, and cybersecurity presents special challenges. Because cybersecurity issues are often subtle, where the adversarial model and details matter greatly, it is challenging to construct MCQs for which there is exactly one best but non-obvious answer. We hope that our experiences and lessons learned may help others create more effective concept inventories and assessments in STEM.

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arXiv2020

Formal Methods Analysis of the Secure Remote Password Protocol

We analyze the Secure Remote Password (SRP) protocol for structural weaknesses using the Cryptographic Protocol Shapes Analyzer (CPSA) in the first formal analysis of SRP (specifically, Version 3). SRP is a widely deployed Password Authenticated Key Exchange (PAKE) protocol used in 1Password, iCloud Keychain, and other products. As with many PAKE protocols, two participants use knowledge of a pre-shared password to authenticate each other and establish a session key. SRP aims to resist dictionary attacks, not store plaintext-equivalent passwords on the server, avoid patent infringement, and avoid export controls by not using encryption. Formal analysis of SRP is challenging in part because existing tools provide no simple way to reason about its use of the mathematical expression $v + g^b \mod q$. Modeling $v + g^b$ as encryption, we complete an exhaustive study of all possible execution sequences of SRP. Ignoring possible algebraic attacks, this analysis detects no major structural weakness, and in particular no leakage of any secrets. We do uncover one notable weakness of SRP, which follows from its design constraints. It is possible for a malicious server to fake an authentication session with a client, without the client's participation. This action might facilitate an escalation of privilege attack, if the client has higher privileges than does the server. We conceived of this attack before we used CPSA and confirmed it by generating corresponding execution shapes using CPSA.

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arXiv2019

Investigating Crowdsourcing to Generate Distractors for Multiple-Choice Assessments

We present and analyze results from a pilot study that explores how crowdsourcing can be used in the process of generating distractors (incorrect answer choices) in multiple-choice concept inventories (conceptual tests of understanding). To our knowledge, we are the first to propose and study this approach. Using Amazon Mechanical Turk, we collected approximately 180 open-ended responses to several question stems from the Cybersecurity Concept Inventory of the Cybersecurity Assessment Tools Project and from the Digital Logic Concept Inventory. We generated preliminary distractors by filtering responses, grouping similar responses, selecting the four most frequent groups, and refining a representative distractor for each of these groups. We analyzed our data in two ways. First, we compared the responses and resulting distractors with those from the aforementioned inventories. Second, we obtained feedback from Amazon Mechanical Turk on the resulting new draft test items (including distractors) from additional subjects. Challenges in using crowdsourcing include controlling the selection of subjects and filtering out responses that do not reflect genuine effort. Despite these challenges, our results suggest that crowdsourcing can be a very useful tool in generating effective distractors (attractive to subjects who do not understand the targeted concept). Our results also suggest that this method is faster, easier, and cheaper than is the traditional method of having one or more experts draft distractors, and building on talk-aloud interviews with subjects to uncover their misconceptions. Our results are significant because generating effective distractors is one of the most difficult steps in creating multiple-choice assessments.

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arXiv2019

PPT: New Low Complexity Deterministic Primality Tests Leveraging Explicit and Implicit Non-Residues. A Set of Three Companion Manuscripts

In this set of three companion manuscripts/articles, we unveil our new results on primality testing and reveal new primality testing algorithms enabled by those results. The results have been classified (and referred to) as lemmas/corollaries/claims whenever we have complete analytic proof(s); otherwise the results are introduced as conjectures. In Part/Article 1, we start with the Baseline Primality Conjecture~(PBPC) which enables deterministic primality detection with a low complexity = O((log N)^2) ; when an explicit value of a Quadratic Non Residue (QNR) modulo-N is available (which happens to be the case for an overwhelming majority = 11/12 = 91.67% of all odd integers). We then demonstrate Primality Lemma PL-1, which reveals close connections between the state-of-the-art Miller-Rabin method and the renowned Euler-Criterion. This Lemma, together with the Baseline Primality Conjecture enables a synergistic fusion of Miller-Rabin iterations and our method(s), resulting in hybrid algorithms that are substantially better than their components. Next, we illustrate how the requirement of an explicit value of a QNR can be circumvented by using relations of the form: Polynomial(x) mod N = 0 ; whose solutions implicitly specify Non Residues modulo-N. We then develop a method to derive low-degree canonical polynomials that together guarantee implicit Non Residues modulo-N ; which along with the Generalized Primality Conjectures enable algorithms that achieve a worst case deterministic polynomial complexity = O( (log N)^3 polylog(log N)) ; unconditionally ; for any/all values of N. In Part/Article 2 , we present substantial experimental data that corroborate all the conjectures. No counter example has been found. Finally in Part/Article 3, we present analytic proof(s) of the Baseline Primality Conjecture that we have been able to complete for some special cases.

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arXiv2019

The CATS Hackathon: Creating and Refining Test Items for Cybersecurity Concept Inventories

For two days in February 2018, 17 cybersecurity educators and professionals from government and industry met in a "hackathon" to refine existing draft multiple-choice test items, and to create new ones, for a Cybersecurity Concept Inventory (CCI) and Cybersecurity Curriculum Assessment (CCA) being developed as part of the Cybersecurity Assessment Tools (CATS) Project. We report on the results of the CATS Hackathon, discussing the methods we used to develop test items, highlighting the evolution of a sample test item through this process, and offering suggestions to others who may wish to organize similar hackathons. Each test item embodies a scenario, question stem, and five answer choices. During the Hackathon, participants organized into teams to (1) Generate new scenarios and question stems, (2) Extend CCI items into CCA items, and generate new answer choices for new scenarios and stems, and (3) Review and refine draft CCA test items. The CATS Project provides rigorous evidence-based instruments for assessing and evaluating educational practices; these instruments can help identify pedagogies and content that are effective in teaching cybersecurity. The CCI measures how well students understand basic concepts in cybersecurity---especially adversarial thinking---after a first course in the field. The CCA measures how well students understand core concepts after completing a full cybersecurity curriculum.

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arXiv2018

Phishing in an Academic Community: A Study of User Susceptibility and Behavior

We present an observational study on the relationship between demographic factors and phishing susceptibility at the University of Maryland, Baltimore County (UMBC). In spring 2018, we delivered phishing attacks to 450 randomly-selected students on three different days (1,350 students total) to examine user click rates and demographics among UMBC's undergraduates. Participants were initially unaware of the study. Experiment 1 claimed to bill students; Experiment 2 enticed users with monetary rewards; and Experiment 3 threatened users with account cancellation. We found correlations resulting in lowered susceptibility based on college affiliation, academic year progression, cyber training, involvement in cyber clubs or cyber scholarship programs, time spent on the computer, and age demographics. We found no significant correlation between gender and susceptibility. Contrary to our expectations, we observed greater user susceptibility with greater phishing knowledge and awareness. Students who identified themselves as understanding the definition of phishing had a higher susceptibility than did their peers who were merely aware of phishing attacks, with both groups having a higher susceptibility than those with no knowledge of phishing. Approximately 59% of subjects who opened the phishing email clicked on its phishing link, and approximately 70% of those subjects who additionally answered a demographic survey clicked.

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arXiv2018

On the Origins and Variations of Blockchain Technologies

We explore the origins of blockchain technologies to better understand the enduring needs they address. We identify the five key elements of a blockchain, show embodiments of these elements, and examine how these elements come together to yield important properties in selected systems. To facilitate comparing the many variations of blockchains, we also describe the four crucial roles of blockchain participants common to all blockchains. Our historical exploration highlights the 1979 work of David Chaum whose vault system embodies many of the elements of blockchains.

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arXiv2017

Creating a Cybersecurity Concept Inventory: A Status Report on the CATS Project

We report on the status of our Cybersecurity Assessment Tools (CATS) project that is creating and validating a concept inventory for cybersecurity, which assesses the quality of instruction of any first course in cybersecurity. In fall 2014, we carried out a Delphi process that identified core concepts of cybersecurity. In spring 2016, we interviewed twenty-six students to uncover their understandings and misconceptions about these concepts. In fall 2016, we generated our first assessment tool--a draft Cybersecurity Concept Inventory (CCI), comprising approximately thirty multiple-choice questions. Each question targets a concept; incorrect answers are based on observed misconceptions from the interviews. This year we are validating the draft CCI using cognitive interviews, expert reviews, and psychometric testing. In this paper, we highlight our progress to date in developing the CCI. The CATS project provides infrastructure for a rigorous evidence-based improvement of cybersecurity education. The CCI permits comparisons of different instructional methods by assessing how well students learned the core concepts of the field (especially adversarial thinking), where instructional methods refer to how material is taught (e.g., lab-based, case-studies, collaborative, competitions, gaming). Specifically, the CCI is a tool that will enable researchers to scientifically quantify and measure the effect of their approaches to, and interventions in, cybersecurity education.

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