Cryptology ePrint Archive: Report 2020/224
Security under Message-Derived Keys: Signcryption in iMessage
Mihir Bellare and Igors Stepanovs
Abstract: At the core of Apple's iMessage is a signcryption scheme that involves symmetric encryption of a message under a key that is derived from the message itself. This motivates us to formalize a primitive we call Encryption under Message-Derived Keys (EMDK). We prove security of the EMDK scheme underlying iMessage. We use this to prove security of the signcryption scheme itself, with respect to definitions of signcryption we give that enhance prior ones to cover issues peculiar to messaging protocols. Our provable-security results are quantitative, and we discuss the practical implications for iMessage.
Category / Keywords: cryptographic protocols / Signcryption, Public-Key Encryption, Symmetric Encryption, Random Oracle Model, Messaging
Original Publication (with major differences): IACR-EUROCRYPT-2020
Date: received 19 Feb 2020, last revised 3 Mar 2020
Contact author: istepanovs at inf ethz ch,mihir@eng ucsd edu
Available format(s): PDF | BibTeX Citation
Version: 20200303:110117 (All versions of this report)
Short URL: ia.cr/2020/224
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