Abstract. We identify and fill some gaps with regard to consistency (the extent to which false positives are produced) for public-key encryption with keyword search (PEKS). We define computational and statistical relaxations of the existing notion of perfect consistency, show that the scheme of [7] is computationally consistent, and provide a new scheme that is statistically consistent. We also provide a transform of an anonymous IBE scheme to a secure PEKS scheme that, unlike the previous one, guarantees consistency. Finally we suggest three extensions of the basic notions considered here, namely anonymous HIBE, public-key encryption with temporary keyword search, and identity-based encryption with keyword search.

Password-based authenticated key exchange (PAKE) are protocols which are designed to be secure even when the secret key used for authentication is a human-memorable password. In this paper, we consider PAKE protocols in the three-party scenario, in which the users trying to establish a common secret do not share a password between themselves but only with a trusted server. Towards our goal, we recall some of the existing security notions for PAKE protocols and introduce new ones that are more suitable to the case of generic constructions of three-party protocols. We then present a natural generic construction of a three-party PAKE protocol from any two-party PAKE protocol and prove its security. To the best of our knowledge, the new protocol is the first provably-secure PAKE protocol in the three-party setting.

Abstract. This paper provides security analysis for the public-key encryption scheme DHIES (formerly named DHES and DHAES), which was proposed in [7] and is now in several draft standards. DHIES is a Diffie-Hellman based scheme that combines a symmetric encryption method, a message authentication code, and a hash function, in addition to number-theoretic operations, in a way which is intended to provide security against chosen-ciphertext attacks. In this paper we find natural assumptions under which DHIES achieves security under chosen-ciphertext attack. The assumptions we make about the Diffie-Hellman problem are interesting variants of the customary ones, and we investigate relationships among them, and provide security lower bounds. Our proofs are in the standard model; no random-oracle assumption is required.

International audienceFunctional encryption is a new paradigm in public-key encryption that allows users to finely control the amount of information that is revealed by a ciphertext to a given receiver. Recent papers have focused their attention on constructing schemes for general functionalities at expense of efficiency. Our goal, in this paper, is to construct functional encryption schemes for less general functionalities which are still expressive enough for practical scenarios. We propose a functional encryption scheme for the inner-product functionality, meaning that decrypting an encrypted vector x with a key for a vector y will reveal only ⟨x,y⟩ and noth- ing else, whose security is based on the DDH assumption. Despite the simplicity of this functionality, it is still useful in many contexts like descriptive statistics. In addition, we generalize our approach and present a generic scheme that can be instantiated, in addition, under the LWE assumption and offers various trade-offs in terms of expressiveness and efficiency