Ari Juels

Ari Juels
Alma mater	University of California, Berkeley (PhD, 1996)
Known for	Proof of work Client puzzles Blockchain oracles (Town Crier, DECO) Maximal extractable value Proofs of retrievability Fuzzy cryptography
Scientific career
Fields	Cryptography Blockchain Information security
Institutions	Cornell Tech Chainlink Labs IC3
Website	arijuels.com

Ari Juels is an American Cryptographer. As of 2025 ^[update] , he is currently the Weill Family Foundation and Joan and Sanford I. Weill Professor at Cornell Tech and the co-director at the Initiative for CryptoCurrencies and Contracts. ^[1]

He is also the chief scientist at Chainlink Labs. ^[2] He co-authored the first Chainlink white paper in 2017 with Sergey Nazarov and Steve Ellis. ^[3] The smallest denomination of the LINK token, the Juel, is named in his honor. ^[4]

Juels was an employee of RSA Security from 1996 until 2013, with the title Chief Scientist starting in 2007. ^[5]

On January 20, 2022, he testified before the United States House Energy Subcommittee on Oversight and Investigations regarding the Environmental impact of the cryptocurrency industry. ^[1]

His best known co-authored results in cryptography and information security include:

• Proof of work (1999): Coined and formalized the term in work that predated and influenced its later use by Satoshi Nakamoto in the Bitcoin whitepaper. ^[6]

• Client puzzles (1999): Developed proof-of-work-based countermeasures against denial-of-service attacks that are widely used today. ^{[7] [8]}

• Fuzzy cryptography (1999, 2006): Co-developed error-tolerant cryptographic primitives—fuzzy commitment schemes and fuzzy vaults—for securing noisy data such as biometric templates. ^{[9] [10]}

• Privacy-preserving targeted advertising (2001): Proposed the first protocols for targeted advertising that preserve user privacy. ^[11]

• Coercion-resistant voting (2005): Introduced the concept of coercion-resistance, which has become a standard security property for electronic voting systems designed to resist bribery and voter coercion. ^[12]

• Social recovery (2006): Introduced social recovery mechanisms for credential restoration using trusted social connections, sometimes called "fourth-factor authentication." ^[13]

• RFID and NFC security (2003–2009): Developed security technologies for RFID and NFC tags, including the "blocker tag" privacy-protection mechanism ^[14] and soft blocking techniques, ^[15] as well as an influential survey paper on RFID security and privacy. ^[16]

• Proofs of retrievability (PoRs) (2007): Introduced the first efficient cryptographic technique for verifying the complete availability and integrity of remotely stored files in cloud storage systems. ^[17]

• Blockchain oracles (2016, 2020): Developed Town Crier, the first blockchain oracle system using trusted execution environments, ^[18] and DECO, a cryptographic oracle protocol. ^[19] Both privacy-preserving systems have been deployed by Chainlink. ^{[20] [21]}

• Model-extraction attacks (2016): Introduced the concept of adversarial attacks that steal machine learning models through strategic queries. ^[22]

• Maximal extractable value (2020): Coined the term "miner extractable value" (MEV, later generalized to "maximal extractable value") and initiated its systematic study, contributing to the foundation of what has become a significant market in blockchain systems. ^[23]

Juels has published two thriller novels: Tetraktys (2009), a cryptography thriller, ^[24] and The Oracle (2024), a cryptocurrency and blockchain thriller. ^{[25] [26] [27] [28]}

References

1. "Cornell Tech professor tells Congress crypto can go greener | Cornell Chronicle". news.cornell.edu. Retrieved 2025-10-18.
2. "Chainlink Labs' chief scientist on 'misleading' narratives tied to merging AI and blockchain". CNBC. 2024-04-10. Retrieved 2025-10-18.
3. Ellis, Steven; Juels, Ari; Nazarov, Sergey (4 September 2017). "ChainLink A Decentralized Oracle Network". chain.link. Archived from the original (paper) on 6 October 2017. Retrieved 8 October 2022.
4. "LINK Token Contracts". Chainlink Documentation. Chainlink Labs. Retrieved 2025-11-29.
5. Brett, Charles (2020-09-04). "Chainlink acquires DECO from Cornell". Enterprise Times. Retrieved 2025-10-18.
6. Jakobsson, Markus; Juels, Ari (September 1999). Proofs of Work and Bread Pudding Protocols. IFIP TC6/TC11 Joint Working Conference on Secure Information Networks: Communications and Multimedia Security. Boston, MA: Springer. pp. 258–272. doi:10.1007/978-0-387-35568-9_18.
7. Juels, Ari; Brainard, John (February 1999). Client Puzzles: A Cryptographic Defense Against Connection Depletion Attacks. Proceedings of the 1999 ISOC Network and Distributed System Security Symposium. pp. 151–165.
8. Tatoris, Reid; Wolters, Benedikt (April 1, 2022). "The end of the road for Cloudflare CAPTCHAs". Cloudflare Blog. Retrieved 2024-12-06. Challenges are selected based on what characteristics the visitor emits and based on the initial information we have about the visitor. Those challenges include, but are not limited to, proof-of-work, proof-of-space, probing for web APIs, and various challenges for detecting browser-quirks and human behavior.
9. Juels, Ari; Wattenberg, Martin (November 1999). A Fuzzy Commitment Scheme. Proceedings of the 6th ACM Conference on Computer and Communications Security. pp. 28–36. doi: 10.1145/319709.319714 .
10. Juels, Ari; Sudan, Madhu (2006). "A Fuzzy Vault Scheme". Designs, Codes and Cryptography. 38 (2): 237–257. doi:10.1007/s10623-005-6343-z.
11. Juels, Ari (2001). Naccache, David (ed.). Targeted Advertising ... and Privacy Too. Topics in Cryptology – CT-RSA 2001. Lecture Notes in Computer Science. Vol. 2020. Berlin, Heidelberg: Springer. pp. 408–424. doi:10.1007/3-540-45353-9_30.
12. Juels, Ari; Catalano, Dario; Jakobsson, Markus (November 2005). Coercion-Resistant Electronic Elections. Proceedings of the 2005 ACM Workshop on Privacy in the Electronic Society. pp. 61–70. doi:10.1145/1102199.1102213.
13. Brainard, John G.; Juels, Ari; Rivest, Ronald L.; Szydlo, Michael; Yung, Moti (October 2006). Fourth-Factor Authentication: Somebody You Know. Proceedings of the 13th ACM Conference on Computer and Communications Security. pp. 168–178. doi:10.1145/1180405.1180427.
14. Juels, Ari; Rivest, Ronald L.; Szydlo, Michael (2003). The Blocker Tag: Selective Blocking of RFID Tags for Consumer Privacy. Proceedings of the 10th ACM Conference on Computer and Communications Security. CCS '03. ACM. pp. 103–111. doi:10.1145/948109.948126.
15. Juels, Ari; Brainard, John (2004). Soft Blocking: Flexible Blocker Tags on the Cheap. Proceedings of the 2004 ACM Workshop on Privacy in the Electronic Society. WPES '04. ACM. pp. 1–7. doi:10.1145/1029179.1029181.
16. Juels, Ari (February 2006). "RFID Security and Privacy: A Research Survey". IEEE Journal on Selected Areas in Communications. 24 (2): 381–394. doi:10.1109/JSAC.2005.861395.
17. Juels, Ari; Kaliski, Burton S. (October 2007). PORs: Proofs of Retrievability for Large Files. Proceedings of the 14th ACM Conference on Computer and Communications Security. pp. 584–597. doi:10.1145/1315245.1315317.
18. Zhang, Fan; Cecchetti, Ethan; Croman, Kyle; Juels, Ari; Shi, Elaine (October 2016). Town Crier: An Authenticated Data Feed for Smart Contracts. Proceedings of the 2016 ACM SIGSAC Conference on Computer and Communications Security. pp. 270–282. doi: 10.1145/2976749.2978326 .
19. Zhang, Fan; Maram, Deepak; Malvai, Harjasleen; Goldfeder, Steven; Juels, Ari (November 2020). DECO: Liberating Web Data Using Decentralized Oracles for TLS. Proceedings of the 2020 ACM SIGSAC Conference on Computer and Communications Security. pp. 1919–1938.
20. Keynote by Sergey Nazarov of Chainlink. Chainlink. Retrieved 2024-12-06– via SmartCon.
21. "DECO Sandbox: Privacy-Preserving Data Verification". Chainlink. Retrieved 2024-12-06.
22. Tramèr, Florian; Zhang, Fan; Juels, Ari; Reiter, Michael K.; Ristenpart, Thomas (August 2016). Stealing Machine Learning Models via Prediction APIs. Proceedings of the 25th USENIX Security Symposium. pp. 601–618.
23. Daian, Philip; Goldfeder, Steven; Kell, Tyler; Li, Yunqi; Zhao, Xueyuan; Bentov, Iddo; Breidenbach, Lorenz; Juels, Ari (May 2020). Flash Boys 2.0: Frontrunning in Decentralized Exchanges, Miner Extractable Value, and Consensus Instability. 2020 IEEE Symposium on Security and Privacy. pp. 910–927. doi:10.1109/SP40000.2020.00040.
24. "The 2010 International Book Awards Results". International Book Awards. Retrieved 2024-12-06.
25. "New Thriller from Cornell's Ari Juels Imagines Weaponizing Blockchain". Bloomberg. 2024-02-15. Retrieved 2024-12-06.
26. "What's at the Intersection of Crypto and AI? Perhaps Murder". CoinDesk. 2024-03-01. Retrieved 2024-12-06.
27. Juels, Ari (2024). The Oracle. New York: Skyhorse Publishing Talos. ISBN   978-1-945863-85-1.
28. Juels, Ari (2009). Tetraktys. Emerald Bay Books. ISBN   9780982283707.