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• The proposed puncturable identity-based matchmaking key encapsulation mechanism (PIB-MKEM) enables a receiver to revoke his decapsulation capacity individually, and further be convinced that the received ciphertext comes from an authorized sender. • The proposed 0-RTT FSMAKE protocol based on PIB-MKEM is the first 0-RTT key exchange protocol that simultaneously enjoys forward secrecy and mutual authentication. • The concrete construction of PIB-MKEM is proved to be secure in the random oracle model, and provides a trade-off between computation overhead and storage cost. Instant messaging applications like WhatsApp and iMessage have been widely used to exchange public and private information for both individuals and organizations. At the same time, the asynchronicity nature of these applications also introduces various security issues. To this end, considerable efforts have been made to strengthen the security and privacy of these applications, where a major goal is to capture the forward secrecy of asynchronous messaging without sacrificing other reasonable security properties. In this paper, we mainly focus on forward-secure zero round-trip time (0-RTT) key exchange protocols. Such a protocol enables a user to send the encrypted application data along with the first protocol message, and thus is especially suitable for securing asynchronous messaging. Concretely, we introduce a new cryptographic primitive dubbed as puncturable identity-based matchmaking key encapsulation mechanism (PIB-MKEM). It captures the authenticity of ciphertexts, and also allows a receiver to repeatedly update his/her secret key with a puncture algorithm. Based on PIB-MKEM, we further put forth a generic construction of 0-RTT key exchange protocol that enjoys forward secrecy and mutual authentication as well as replay resistance in parallel. We also present a concrete construction of PIB-MKEM, which immediately instantiates the above generic 0-RTT key exchange protocol. Moreover, we implement the proposed PIB-MKEM construction, and provide extensive evaluations to demonstrate its practicability. [ABSTRACT FROM AUTHOR]

Symmetric Searchable Encryption (SSE) realizes to outsource data to an untrusted server privately. Dynamic SSE (DSSE) is a practical application which supports data addition and deletion. However, these update operations incur leakage during search and update queries. Therefore, forward and backward privacy were introduced to address the update and search operation leakage in DSSE. Forward privacy was extensively studied in the literature. Backward privacy with three types of revealing level was studied little. The strongest backward privacy was achieved by the expensive tools, impractical! Wheras the practical DSSEs gained weak backward privacy only. In this paper, we present a practical DSSE scheme to achieve stronger backward security—backward privacy with update pattern. We take advantage of key-homomorphic pseudorandom functions and our scheme requires only 1 roundtrip to get search result. [ABSTRACT FROM AUTHOR]

Dynamic Searchable Symmetric Encryption (DSSE) has gained increasing popularity as it enables users to perform both file updates and ciphertext retrieval over encrypted data. However, existing DSSE schemes still lead to privacy leakage (e.g., forward and backward privacy) in the dynamic setting. Some forward and backward secure DSSE schemes have been proposed, but still cannot support the keyword shielding flexibly. To solve this challenging issue, we propose a Forward and Backward Authorized Keyword Search (FB-AKS) scheme with recoverable keyword shielding by using trapdoor permutations and puncturable encryption in this paper. Compared with existing forward and backward private schemes, FB-AKS achieves keyword authorization flexibly (e.g., keyword shielding, keyword un-shielding). The formal security analysis proves that FB-AKS achieves forward and backward security. And extensive experiments demonstrate that FB-AKS has less computation and storage overheads. [ABSTRACT FROM AUTHOR]