Ashwin Jha

Symmetric Cryptography MC 1.40
Faculty of Computer Science
Ruhr-University of Bochum
Universitätsstr. 150
44801 Bochum, Germany
ashwin.jha@ruhr-uni-bochum.de

I am a postdoc in Prof. Gregor Leander's group at RUB since January 2024. Previously, I was a postdoc at CISPA from January 2021 to December 2023.

I received my PhD in Computer Science from ISI Kolkata in June 2020, where I worked on the provable security of symmetric-key cryptographic schemes under the supervision of Prof. Mridul Nandi. Before that, I completed my masters in Computer Science at ISI Kolkata, focusing on the cryptanalysis of iterated hash function and its variants. I received my bachelors degree in Computer Engineering from the University of Delhi.

My research interests lie primarily in cryptography, particularly in the analysis of symmetric-key modes of operations. I study their provable security against classical and post-quantum adversaries. My CV is available here.

Publications
  1. 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)
  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. 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)
  4. 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
  5. On TRP-RF Switch in the Quantum Query Model
    Ashwin Jha
    IACR Commun. Cryptol. 2(2): 11 (2025)
  6. Generic Security Analysis of GCM-SST
    Akiko Inoue, Ashwin Jha, Bart Mennink, Kazuhiko Minematsu
    Proceedings (Part II) of ACNS 2025: 342-369 (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. A Note on the Generalized Sum-Capture Problem for Rings
    Ashwin Jha
  10. 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)
  11. 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)
  12. 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)
  13. On Quantum Secure Compressing Pseudorandom Functions
    Ritam Bhaumik, Benoît Cogliati, Jordan Ethan, Ashwin Jha
    Proceedings (Part III) of ASIACRYPT 2023: 34-66 (2023)
  14. 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)
  15. Subverting Telegram’s End-to-End Encryption
    Benoît Cogliati, Jordan Ethan, Ashwin Jha
    IACR Transactions on Symmetric Cryptology 2023(1): 5-40 (2023)
  16. Towards Tight Security Bounds for OMAC, XCBC and TMAC
    Soumya Chattopadhyay, Ashwin Jha, Mridul Nandi
    Proceedings (Part I) of ASIACRYPT 2022: 348-378 (2022)
  17. A Survey on Applications of H-Technique: Revisiting Security Analysis of PRP and PRF
    Ashwin Jha, Mridul Nandi
    Entropy 24(4): 462 (2022)
  18. 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)
  19. 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)
  20. tHyENA: Making HyENA Even Smaller
    Avik Chakraborti, Nilanjan Datta, Ashwin Jha, Cuauhtemoc Mancillas-López, Mridul Nandi
    Proceedings of INDOCRYPT 2021: 26-48 (2021)
  21. Revisiting the Security of COMET Authenticated Encryption Scheme
    Shay Gueron, Ashwin Jha, Mridul Nandi
    Proceedings of INDOCRYPT 2021: 3-25 (2021)
  22. Fine-tuning the ISO/IEC Standard LightMAC
    Soumya Chattopadhyay, Ashwin Jha, Mridul Nandi
    Proceedings (Part III) of ASIACRYPT 2021: 490-519 (2021)
  23. On Length Independent Security Bounds for the PMAC Family
    Bishwajit Chakraborty, Soumya Chattopadhyay, Ashwin Jha, Mridul Nandi
    IACR Transactions on Symmetric Cryptology 2021(2): 423-445 (2021)
  24. How to Build Optimally Secure PRFs Using Block Ciphers
    Benoît Cogliati, Ashwin Jha, Mridul Nandi
    Proceedings (Part I) of ASIACRYPT 2020: 754-784 (2020)
  25. On the Security of Sponge-type Authenticated Encryption Modes
    Bishwajit Chakraborty, Ashwin Jha, Mridul Nandi
    IACR Transactions on Symmetric Cryptology 2020(2): 93-119 (2020)
  26. From Combined to Hybrid: Making Feedback-based AE even Smaller
    Avik Chakraborti, Nilanjan Datta, Ashwin Jha, Snehal Mitragotri, Mridul Nandi
    IACR Transactions on Symmetric Cryptology 2020(S1): 417-445 (2020)
  27. ESTATE: A Lightweight and Low Energy Authenticated Encryption Mode
    Avik Chakraborti, Nilanjan Datta, Ashwin Jha, Cuauhtemoc Mancillas-López, Mridul Nandi, Yu Sasaki
    IACR Transactions on Symmetric Cryptology 2020(S1): 350-389 (2020)
  28. Tight Security of Cascaded LRW2
    Ashwin Jha, Mridul Nandi
    Journal of Cryptology 33(3): 1272-1317 (2020)
  29. On Random Read Access in OCB
    Ashwin Jha, Cuauhtemoc Mancillas-López, Mridul Nandi, Sourav Sen Gupta
    IEEE Transactions on Information Theory 65(12): 8325-8344 (2019)
  30. INT-RUP Secure Lightweight Parallel AE Modes
    Avik Chakraborti, Nilanjan Datta, Ashwin Jha, Cuauhtemoc Mancillas-López, Mridul Nandi, Yu Sasaki
    IACR Transactions on Symmetric Cryptology 2019(4): 81-118 (2019)
  31. On Rate-1 and Beyond-the-Birthday Bound Secure Online Ciphers using Tweakable Block Ciphers
    Ashwin Jha, Mridul Nandi
    Cryptography and Communications 10(5): 731-753 (2018)
  32. 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)
  33. Tight Security Analysis of EHtM MAC
    Avijit Dutta, Ashwin Jha, Mridul Nandi
    IACR Transactions on Symmetric Cryptology 2017(3): 130-150 (2017)
  34. On the Exact Security of Message Authentication using Pseudorandom Functions
    Ashwin Jha, Avradip Mandal, Mridul Nandi
    IACR Transactions on Symmetric Cryptology 2017(1): 427-448 (2017)
  35. A New Look at Counters: Don't Run Like Marathon in a Hundred Meter Race
    Avijit Dutta, Ashwin Jha, Mridul Nandi
    IEEE Transactions on Computers 66(11): 1851-1864 (2017)
  36. Exact Security Analysis of Hash-then-Mask Type Probabilistic MAC Constructions
    Avijit Dutta, Ashwin Jha, Mridul Nandi
    IACR Cryptology ePrint Archive Report 2016/983 (2016)
  37. Revisiting Structure Graph: Applications to CBC-MAC and EMAC
    Ashwin Jha, Mridul Nandi
    Journal of Mathematical Cryptology 10(3-4): 157-180 (2016)
  38. Some Cryptanalytic Results on Zipper Hash and Concatenated Hash
    Ashwin Jha, Mridul Nandi
    IACR Cryptology ePrint Archive Report 2015/973 (2015)
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