Featured topics: Timelock Encryption, Witness Encryption, Deniable Encryption.
Structure: Welcome/introduction; two invited talks; break; one invited talk and a panel conversation.
Date and time: January 16th, 2025, 12:00–16:00 EST (UTC -5). (Subject to modifications)
Location: Virtual event (video conference).
Attendance: Open and free to the public, upon registration.
Format: Webinar (presenters can share video and audio; attendees can use text for questions and comments).
STPPA7 Schedule:
Times displayed in EST = UTC-5 (EST = Eastern Standard Time; UTC = Coordinated Universal Time)
(Based on text provided by the speakers/panelists, with possible adaptations/abbreviations for conciseness and consistency; see possible links for extended bios)
Organization: The STPPA series is hosted by the NIST Privacy-Enhancing Cryptography (PEC) project. The PEC team (Luís Brandão, Angela Robinson, René Peralta) and all speakers (mentioned above) participated in the panel conversation. Angela Robinson introduced two talks/speakers. The STPPA7 event was organized by Luís Brandão, who also opened the event and introduced one talk/speaker. The virtual event (webinar) received around 215 registrations, of which around 115 attended at least 30 minutes, and around 90 attended more than 90 minutes.
About STPPA: In the "Special Topics on Privacy and Public Auditability" series, the NIST privacy-enhancing cryptography (PEC) project hosts talks on various interconnected topics related to privacy and public auditability. A main goal of the STPPA series is to gather reference material about "PEC tools", which may facilitate future reflections on aspects of standardization and of development of recommendations/guidelines about advanced cryptography, namely for uses related to privacy and public auditability. Each event intends to convey basic technical background, incite curiosity, suggest research questions and discuss applications, with an emphasis on the role of cryptographic tools.
Code of conduct: Attending an STPPA event requires abiding to the Code of Conduct for NIST Conferences.
Selected Presentations | |
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January 16, 2025 | Type |
12:00 PM
STPPA #7 Welcome and Introduction Abstract. Welcome to STPPA#7: the 7th event of the Special Topics on Privacy and Public Auditability (STPPA)! This event explores the theme of "Special Types of Encryption", with talks on timelock encryption, witness encryption, deniable encryption and functional encryption. This brief talk opens the event, introduces the context of the hosting "Privacy Enhancing Cryptography" (PEC) project, welcomes the speakers, and presents the schedule. |
Presentation |
12:15 PM
Timelock Encryption: an Overview and Retrospective Kelsey Melissaris - Aarhus University (Denmark) Yolan Romailler - Randamu Inc (Switzerland and USA) Abstract. This talk presents an overview of timelock encryption (TLE), a cryptographic primitive which secures messages until some point in the future specified during encryption. We review definitions, motivations, applications, and discuss trade offs between two popular timelocking techniques: puzzle-based and authority-based. We then present an authority-based TLE from the identity-based encryption (IBE) scheme of Boneh and Franklin, which is in turn constructed from BLS signatures. Our instantiation leverages threshold BLS to replace the trusted IBE authority with a network of parties, each of whom is potentially malicious. The accompanying implementation is built upon the League of Entropy, a threshold network that acts as our decentralized authority via its public randomness beacon service. The details of this TLE construction and implementation are provided. Finally, in retrospect, we discuss the practical challenges of this implementation and address relevant standardization efforts. We also briefly mention our ongoing work to efficiently boost the applicability of this TLE scheme. Joint work with Nicolas Gailly (Lagrange Labs) Suggested readings: ia.cr/2023/189 |
Presentation |
1:00 PM
Witness Encryption: Theory and Practice Sanjam Garg - University of California, Berkeley (USA) Abstract. In this talk, I will introduce the notion of Witness Encryption and discuss known general constructions. Next, I will discuss efficient special-purpose witness encryption schemes and their applications. Joint work with Chongwon Cho, Nico Döttling, Sanjam Garg, Craig Gentry, Divya Gupta, Mohammad Hajiabadi, Yuval Ishai, Giulio Malavolta,Peihan Miao, Tamer Mour, Rafail Ostrovsky, Antigoni Polychroniadou, Amit Sahai, Akshayaram Srinivasan, and Brent Waters Suggested readings: ia.cr/2013/258 |
Presentation |
2:30 PM
The Multiple Faces of Deniability Rafail Ostrovsky - UCLA (USA) Abstract. I will survey multiple aspects of deniability and related cryptographic notions, including the original deniable encryption paper of Canetti, Dwork, Naor, and Ostrovsky from 1996 and some of the follow-up works on deniable encryption. I will also discuss several related cryptographic notions and how they differ from deniable encryptions. These notions include equivocal encryption and equivocal commitment and their applications in cryptography. Specifically, I will describe applications to non-malleability and adaptive garbling. Finally, I will discuss a related concept of covert multi-party computation and how to construct it. Suggested readings. DOI:10.1007/BFb0052229 |
Presentation |
3:15 PM
STPPA7 Panel Abstract. This will be an informal panel conversation, with the STPPA7 speakers of the talks on timelock encryption, witness encryption, deniable encryption and functional encryption. The panel will reflect on the possible uses of these special types of encryption, and advanced cryptography in general, with a particular emphasis on goals of privacy and public auditability. The reflection will extend to considerations about opportunities, challenges, and visions for the future. |
Presentation |
Starts: January 16, 2025 - 12:00 PM EST
Ends: January 16, 2025 - 04:00 PM EST
Format: Virtual Type: Webinar
Attendance Type: Open to public
Audience Type: Industry,Government,Academia,Other
Security and Privacy: cryptography