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Attribute Based Encryption for Turing Machines from Lattices.

Series: Department Seminar

Speaker: Simran, MS+PhD program student, Computer Science and Engineering, Indian Institute of Technology Madras

Date/Time: Aug 05 11:00:00

Location: CSA Lecture Hall (Room No. 112, Ground Floor)

Abstract:
We provide the first attribute based encryption (ABE) scheme for Turing machines supporting unbounded collusions from lattice assumptions. In more detail, the encryptor encodes an attribute x together with a bound t on the machine running time and a message m into the ciphertext, the key generator embeds a Turing machine M into the secret key and decryption returns m if and only if M(x) = 1. Crucially, the input x and machine M can be of unbounded size, the time bound t can be chosen dynamically for each input and decryption runs in input specific time.

Previously the best known ABE for uniform computation supported only non-deterministic log space Turing machines (NL) from pairings (Lin and Luo, Eurocrypt 2020). In the post-quantum regime, the state of the art supports non-deterministic finite automata from LWE in the symmetric key setting (Agrawal, Maitra and Yamada, Crypto 2019).

Towards our ABE for Turing machines, we obtain the first CP-ABE for circuits of unbounded depth and size from the same assumptions �?? this may be of independent interest.

This is a joint work with Shweta Agrawal (IIT Madras) and Shota Yamada (AIST Tokyo) and will appear in the proceedings of Crypto, 2024.

Speaker Bio:
Simran is a candidate for the MS+PhD program in Computer Science and Engineering at IIT Madras, where she works with Prof. Shweta Agrawal. She completed her Bachelors degree in Mathematics from Delhi University and her Masters in Mathematics and Scientific Computing from NIT Warangal. Her research focuses on developing fundamental and advanced cryptographic protocols, motivated from real world problems, based on lattice-based hardness assumptions which are conjectured to be secure against quantum attacks. Her work includes protocols for enabling fine-grained data access, balancing user anonymity and accountability on communication channels, and providing unconditional security against an authority controlling a setup. During her PhD, she had the opportunity to spend her summers at IIT Delhi (with Venkata Koppula), NTT Tokyo (with Ryo Nishimaki), and IBM Research Lab Bangalore (with Sikhar Patranabis).

Host Faculty: Prof. Chaya Ganesh