Paper 2021/1176
Amortized Threshold Symmetric-key Encryption
Mihai Christodorescu, Sivanarayana Gaddam, Pratyay Mukherjee, and Rohit Sinha
Abstract
Threshold cryptography enables cryptographic operations while keeping the secret keys distributed at all times. Agrawal et al. (CCS'18) propose a framework for Distributed Symmetric-key Encryption (DiSE). They introduce a new notion of Threshold Symmetric-key Encryption (TSE), in that encryption and decryption are performed by interacting with a threshold number of servers. However, the necessity for interaction on each invocation limits performance when encrypting large datasets, incurring heavy computation and communication on the servers. This paper proposes a new approach to resolve this problem by introducing a new notion called Amortized Threshold Symmetric-key Encryption (ATSE), which allows a "privileged" client (with access to sensitive data) to encrypt a large group of messages using a single interaction. Importantly, our notion requires a client to interact for decrypting each ciphertext, thus providing the same security (privacy and authenticity) guarantee as DiSE with respect to a "not-so-privileged" client. We construct an ATSE scheme based on a new primitive that we formalize as flexible threshold key-derivation (FTKD), which allows parties to interactively derive pseudorandom keys in different modes in a threshold manner. Our FTKD construction, which uses bilinear pairings, is based on a distributed variant of left/right constrained PRF by Boneh and Waters (Asiacrypt'13). Despite our use of bilinear maps, our scheme achieves significant speed-ups due to the amortized interaction. Our experiments show 40x lower latency and 30x more throughput in some settings.
Note: Added Page number
Metadata
- Available format(s)
-
PDF
- Category
- Public-key cryptography
- Publication info
- Published elsewhere. Major revision. ACM CCS 2021
- DOI
- 10.1145/3460120.3485256
- Keywords
- Threshold CryptographyConstraint PRFDistributed PRF
- Contact author(s)
- pratyay85 @ gmail com
- History
- 2021-09-17: revised
- 2021-09-14: received
- See all versions
- Short URL
- https://ia.cr/2021/1176
- License
-
CC BY
BibTeX
@misc{cryptoeprint:2021/1176,
author = {Mihai Christodorescu and Sivanarayana Gaddam and Pratyay Mukherjee and Rohit Sinha},
title = {Amortized Threshold Symmetric-key Encryption},
howpublished = {Cryptology {ePrint} Archive, Paper 2021/1176},
year = {2021},
doi = {10.1145/3460120.3485256},
url = {https://eprint.iacr.org/2021/1176}
}