Cryptology ePrint Archive: Report 2021/096

Gladius: LWR based efficient hybrid public key encryption with distributed decryption

Kelong Cong and Daniele Cozzo and Varun Maram and Nigel P. Smart

Abstract: Standard hybrid encryption schemes based on the KEM-DEM framework are hard to implement efficiently in a distributed manner whilst maintaining the CCA security property of the scheme. This is because the DEM needs to be decrypted under the key encapsulated by the KEM, before the whole ciphertext is declared valid. In this paper we present a new variant of the KEM-DEM framework, closely related to Tag-KEMs, which sidesteps this issue. We then present a post-quantum KEM for this framework based on Learning-with-Rounding, which is designed specifically to have fast distributed decryption. Our combined construction of a hybrid encryption scheme with Learning-with-Rounding based KEM, called Gladius, is closely related to the NIST Round 3 candidate called Saber. Finally, we give a prototype distributed implementation that achieves a decapsulation time of 4.99 seconds for three parties.

Category / Keywords: cryptographic protocols /

Date: received 26 Jan 2021, last revised 10 Feb 2021

Contact author: kelong cong at esat kuleuven be, daniele cozzo@kuleuven be, nigel smart@kuleuven be, vmaram@inf ethz ch

Available format(s): PDF | BibTeX Citation

Note: Clarified an issue which was written in a confusing way before

Version: 20210210:163234 (All versions of this report)

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