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International Conference on Advanced Computing and Applications (ACOMP)

Hybrid deniable and short-key encryption protocols based on the authentication procedure

Tan Sy Ho, Alexander Andreevich Moldovyan, Moldovyan Nikolay Andreevich, Canh Ngoc Hoang, Minh Hieu Nguyen, Lich Van Luu, Tien Van Nguyen, Manh Cong Tran

Published Nov 1, 2020• 1 citation

Abstract

To ensure resistance to attacks with coercion to disclose a secret key by an active adversary, the protocol of deniable encryption includes a procedure for mutual authentication of the sender and receiver of a message with their long-term public keys, which is combined with a hidden exchange of single-use public keys used to generate a single-use shared key, on which the secret message is encrypted. Longterm public keys are used to generate a shared secret key, on which a fake message is encrypted. The produced intermediate ciphertexts are converted into a single ciphertext, which is computationally indistinguishable from the ciphertext obtained by probabilistic encryption of a fake message. This approach allows us to build an encryption protocol that is resistant to bi-sided attacks with coercion, since the disclosure of users' private keys gives access only to the fake message and cannot be used to prove the possibility of alternative decryption of the ciphertext transmitted over a public communication channel. The authentication of the single-use public keys is also used to implement protocols for secure encryption using short shared keys.

DOI: 10.1109/acomp50827.2020.00008

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Abstract. The primitive of deniable encryption was first introduced by Canetti et al. (CRYPTO, 1997). Deniable encryption is a regular public key encryption scheme with the added feature that after running the protocol honestly and transmitting a message m, both Sender and Receiver may produce random coins showing that the transmitted ciphertext was an encryption of any message m ′ in the message space. Deniable encryption is a key tool for constructing incoercible protocols, since it allows a party to send one message and later provide apparent evidence to a coercer that a different message was sent. In addition, deniable encryption may be used to obtain adaptively-secure multiparty computation (MPC) protocols and is secure under selective-opening attacks. Different flavors such as sender-deniable and receiver-deniable encryption, where only the Sender or Receiver can produce fake random coins, have been considered. Recently, several open questions regarding the feasibility of deniable encryption have been resolved (c.f. (O’Neill et al., CRYPTO, 2011), (Bendlin et al., ASIACRYPT, 2011)). A fundamental remaining open question is whether it is possible to construct sender-deniable Encryption Schemes with super-polynomial security, where an adversary has negligible advantage in distinguishing real and fake openings. The primitive of simulatable public key encryption (PKE), introduced by Damg˚ard and Nielsen (CRYPTO, 2000), is a public key encryption scheme with additional properties that allow oblivious sampling of public keys and

The notion of deniable authentication protocol was introduced in 1998 by Dwork et al. [11] and Aumann and Rabin [1, 2] independently. As a new cryptographic authentication protocol, a deniable authentication protocol enables an intended receiver to identify the source of a given message without being able to prove the identity of the sender to a third party. Over the past years, many deniable authentication protocols have been proposed. In this paper, we would like to present a universal encrypted deniable authentication protocol from any public key encryption scheme. Provided that the public key encryption scheme is secure, a secure deniable authentication protocol can be directly derived.