Research

My current research programme focuses on practice-oriented provable security of symmetric-key cryptography against both classical and post-quantum adversaries. I am particularly interested in efficient constructions, security models for evolving real-world threats, and statistical and combinatorial tools for obtaining tight security guarantees under minimal assumptions.
More broadly, I am also interested in research questions arising from the interplay between cryptology and its allied fields of cybersecurity, combinatorics, statistics, and complexity theory.

Publications

1. How to Build a Short-Input Random Oracle from Public Random Permutations
   Ritam Bhaumik, Nilanjan Datta, Avijit Dutta, Ashwin Jha, Sougata Mandal, Bart Mennink, Hrithik Nandi, Yaobin Shen
   Proceedings (Part VI) of EUROCRYPT 2026: 394-423 (2026)
2. On the Number of Restricted Solutions to Constrained Systems and their Applications
   Benoît Cogliati, Jordan Ethan, Ashwin Jha, Mridul Nandi, Abishanka Saha
   Proceedings (Part I) of ASIACRYPT 2025: 546-579 (2025)
3. Post-quantum Security of Key-Alternating Feistel Ciphers
   Jyotirmoy Basak, Ritam Bhaumik, Amit Kumar Chauhan, Ravindra Jejurikar, Ashwin Jha, Anandarup Roy, André Schrottenloher, Suprita Talnikar
   Proceedings (Part I) of ASIACRYPT 2025: 446-478 (2025)
4. Cryptographic Treatment of Key Control Security - In Light of NIST SP 800-108
   Ritam Bhaumik, Avijit Dutta, Akiko Inoue, Tetsu Iwata, Ashwin Jha, Kazuhiko Minematsu, Mridul Nandi, Yu Sasaki, Meltem Sönmez Turan, Stefano Tessaro
   Proceedings (Part V) of CRYPTO 2025: 371-403 (2025)
5. Generic Security Analysis of GCM-SST
   Akiko Inoue, Ashwin Jha, Bart Mennink, Kazuhiko Minematsu
   Proceedings (Part II) of ACNS 2025: 342-369 (2025)
6. On TRP-RF Switch in the Quantum Query Model
   Ashwin Jha
   IACR Commun. Cryptol. 2(2): 11 (2025)
7. Towards Optimally Secure Deterministic Authenticated Encryption Schemes
   Yu Long Chen, Avijit Dutta, Ashwin Jha, Mridul Nandi
   Proceedings (Part I) of EUROCRYPT 2025: 3-32 (2025)
8. Mind the Bad Norms - Revisiting Compressed Oracle-Based Quantum Indistinguishability Proofs
   Ritam Bhaumik, Benoît Cogliati, Jordan Ethan, Ashwin Jha
   Proceedings (Part IX) of ASIACRYPT 2024: 215-247 (2024)
9. Tight Security of TNT and Beyond - Attacks, Proofs and Possibilities for the Cascaded LRW Paradigm
   Ashwin Jha, Mustafa Khairallah, Mridul Nandi, Abishanka Saha
   Proceedings (Part I) of EUROCRYPT 2024: 249-279 (2024)
10. On Quantum Secure Compressing Pseudorandom Functions
    Ritam Bhaumik, Benoît Cogliati, Jordan Ethan, Ashwin Jha
    Proceedings (Part III) of ASIACRYPT 2023: 34-66 (2023)
11. On Large Tweaks in Tweakable Even-Mansour with Linear Tweak and Key Mixing
    Benoît Cogliati, Jordan Ethan, Ashwin Jha, Soumya Kanti Saha
    IACR Trans. Symmetric Cryptol. 2023(4): 330--364 (2023)
12. Revisiting Randomness Extraction and Key Derivation Using the CBC and Cascade Modes
    Nianjan Balachandran, Ashwin Jha, Mridul Nandi, Soumit Pal
    IACR Trans. Symmetric Cryptol. 2023(4): 391-419 (2023)
13. Revisiting the Indifferentiability of the Sum of Permutations
    Aldo Gunsing, Ritam Bhaumik, Ashwin Jha, Bart Mennink, Yaobin Shen
    Proceedings (Part III) of CRYPTO 2023: 628-660 (2023)
14. Subverting Telegram’s End-to-End Encryption
    Benoît Cogliati, Jordan Ethan, Ashwin Jha
    IACR Trans. Symmetric Cryptol. 2023(1): 5-40 (2023)
15. Towards Tight Security Bounds for OMAC, XCBC and TMAC
    Soumya Chattopadhyay, Ashwin Jha, Mridul Nandi
    Proceedings (Part I) of ASIACRYPT 2022: 348-378 (2022)
16. Light-OCB: Parallel Lightweight Authenticated Cipher with Full Security
    Avik Chakraborti, Nilanjan Datta, Ashwin Jha, Cuauhtemoc Mancillas-López, Mridul Nandi
    Proceedings of SPACE 2021: 22-41 (2021)
17. Elastic-Tweak: A Framework for Short Tweak Tweakable Block Cipher
    Avik Chakraborti, Nilanjan Datta, Ashwin Jha, Cuauhtemoc Mancillas-López, Mridul Nandi, Yu Sasaki
    Proceedings of INDOCRYPT 2021: 114-137 (2021)
18. Revisiting the Security of COMET Authenticated Encryption Scheme
    Shay Gueron, Ashwin Jha, Mridul Nandi
    Proceedings of INDOCRYPT 2021: 3-25 (2021)
19. tHyENA: Making HyENA Even Smaller
    Avik Chakraborti, Nilanjan Datta, Ashwin Jha, Cuauhtemoc Mancillas-López, Mridul Nandi
    Proceedings of INDOCRYPT 2021: 26-48 (2021)
20. Fine-tuning the ISO/IEC Standard LightMAC
    Soumya Chattopadhyay, Ashwin Jha, Mridul Nandi
    Proceedings (Part III) of ASIACRYPT 2021: 490-519 (2021)
21. On Length Independent Security Bounds for the PMAC Family
    Bishwajit Chakraborty, Soumya Chattopadhyay, Ashwin Jha, Mridul Nandi
    IACR Trans. Symmetric Cryptol. 2021(2): 423-445 (2021)
22. How to Build Optimally Secure PRFs Using Block Ciphers
    Benoît Cogliati, Ashwin Jha, Mridul Nandi
    Proceedings (Part I) of ASIACRYPT 2020: 754-784 (2020)
23. On the Security of Sponge-type Authenticated Encryption Modes
    Bishwajit Chakraborty, Ashwin Jha, Mridul Nandi
    IACR Trans. Symmetric Cryptol. 2020(2): 93-119 (2020)
24. ESTATE: A Lightweight and Low Energy Authenticated Encryption Mode
    Avik Chakraborti, Nilanjan Datta, Ashwin Jha, Cuauhtemoc Mancillas-López, Mridul Nandi, Yu Sasaki
    IACR Trans. Symmetric Cryptol. 2020(S1): 350-389 (2020)
25. From Combined to Hybrid: Making Feedback-based AE even Smaller
    Avik Chakraborti, Nilanjan Datta, Ashwin Jha, Snehal Mitragotri, Mridul Nandi
    IACR Trans. Symmetric Cryptol. 2020(S1): 417-445 (2020)
26. Tight Security of Cascaded LRW2
    Ashwin Jha, Mridul Nandi
    J. Cryptol. 33(3): 1272-1317 (2020)
27. INT-RUP Secure Lightweight Parallel AE Modes
    Avik Chakraborti, Nilanjan Datta, Ashwin Jha, Cuauhtemoc Mancillas-López, Mridul Nandi, Yu Sasaki
    IACR Trans. Symmetric Cryptol. 2019(4): 81-118 (2019)
28. On Random Read Access in OCB
    Ashwin Jha, Cuauhtemoc Mancillas-López, Mridul Nandi, Sourav Sen Gupta
    IEEE Trans. Inf. Theory 65(12): 8325-8344 (2019)
29. On Rate-1 and Beyond-the-Birthday Bound Secure Online Ciphers using Tweakable Block Ciphers
    Ashwin Jha, Mridul Nandi
    Cryptogr. Commun. 10(5): 731-753 (2018)
30. XHX - A Framework for Optimally Secure Tweakable Block Ciphers from Classical Block Ciphers and Universal Hashing
    Ashwin Jha, Eik List, Kazuhiko Minematsu, Sweta Mishra, Mridul Nandi
    Proceedings of LATINCRYPT 2017: 207-227 (2017)
31. Tight Security Analysis of EHtM MAC
    Avijit Dutta, Ashwin Jha, Mridul Nandi
    IACR Trans. Symmetric Cryptol. 2017(3): 130-150 (2017)
32. A New Look at Counters: Don''t Run Like Marathon in a Hundred Meter Race
    Avijit Dutta, Ashwin Jha, Mridul Nandi
    IEEE Trans. Comput. 66(11): 1851-1864 (2017)
33. On the Exact Security of Message Authentication using Pseudorandom Functions
    Ashwin Jha, Avradip Mandal, Mridul Nandi
    IACR Trans. Symmetric Cryptol. 2017(1): 427-448 (2017)
34. Revisiting Structure Graph: Applications to CBC-MAC and EMAC
    Ashwin Jha, Mridul Nandi
    J. Math. Cryptol. 10(3-4): 157-180 (2016)

Preprints / Reports

1. Defining Quantum-Secure Message Authentication
   Ashwin Jha, Mustafa Khairallah, Jannis Leuther, Stefan Lucks
   IACR Cryptol. ePrint Arch. Report 2026/271 (2026)
2. Naor-Reingold goes Beyond-the-Birthday-Bound
   Avik Chakraborti, Bishwajit Chakraborty, Nilanjan Datta, Avijit Dutta, Ashwin Jha, Sougata Mandal, Hrithik Nandi, Mridul Nandi, Abishanka Saha
   IACR Cryptol. ePrint Arch. Report 2025/1486 (2025)
3. A Note on the Generalized Sum-Capture Problem for Rings
   Ashwin Jha
4. A Survey on Applications of H-Technique: Revisiting Security Analysis of PRP and PRF
   Ashwin Jha, Mridul Nandi
   Entropy 24(4): 462 (2022)
5. Provable Security of Symmetric-key Cryptographic Schemes
   Ashwin Jha
   Ph.D. Thesis, ISI Kolkata (2020)
6. Some Cryptanalytic Results on Zipper Hash and Concatenated Hash
   Ashwin Jha, Mridul Nandi
   IACR Cryptol. ePrint Arch. Report 2015/973 (2015)
7. Cryptanalysis of Iterated Hash and Its Variants
   Ashwin Jha
   Master's Thesis, ISI Kolkata (2015)

Academic Services

Selected Invited Talks

1. Constrained Systems
   ASK 2026 (NTU, Singapore)
2. Evasive Properties: A Gap in the Quantum Oracles Zoo
   MAS Seminar (NTU, Singapore)
3. Evasive Properties: A Gap in the Quantum Oracles Zoo
   ASK 2024 (TCG CREST, Kolkata)
4. Reset-Sampling: Fine-tuning the Security of Standardized MACs
   CRC Seminar Series (TII, Abu Dhabi)
5. Towards an Improved Bound on CBC Collision Probability and Its Applications
   India Crypto Meet (Online)

Programme Committees / Editorial Boards

• ACM-CCS 2026, 2025
• ASIACRYPT 2026, 2025
• CANS 2023, 2022
• EUROCRYPT 2027
• SAC 2026
• Trans. Symmetric Cryptol. 2026/27, 2025/26, 2023/24, 2022/23

Organisation

• Co-organiser of the recurring Online GAPS seminar since Feb 2026.
• Co-organiser of GAPS 2025, held in Singapore in September 2025.

Teaching

• Finite Fields: Theory and Algorithms
  Guest-lecturer · RUB · Spring 2026
• Symmetric Cryptanalysis
  Co-lecturer · RUB · Autumn 2025
• Advanced Cryptology
  Co-lecturer · ISI Kolkata · Autumn 2020
• Computing Systems I
  Teaching assistant · ISI Kolkata · Autumn 2018
• Cryptology
  Co-lecturer · ISI Kolkata · Autumn 2018
• Number Theory
  Teaching assistant · ISI Kolkata · Spring 2017
• Data and File Structures Laboratory
  Teaching assistant · ISI Kolkata · Autumn 2015

Contact

I am always happy to hear from motivated students and early-career researchers. Whether you have a specific question related to my current research interests or would simply like to discuss possible directions, please feel free to reach out.