On the Impossibility of Sender-Deniable Public Key Encryption.
Dana Dachman-Soled · 2012
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