Abstract

. Remotely keyed encryption schemes (RKESs), introduced by Blaze [6], support high-bandwidth cryptographic applications (such as encrypted video conferences) in which long-lived secrets (such as users' private keys) never leave lower-bandwidth environments such as secure smart-cards. We provide a formal framework in which to study the security of RKESs and give RKESs that satisfy our formal security requirements. Our RKESs are efficient in that the amount of communication and computation required of the smart-card is independent of the input size. In one proof of security, we use the pseudorandom permutation framework of Naor and Reingold [18] in an essential way. Keywords: Block Ciphers, Pseudorandomness, Remotely Keyed Encryption, Session Keys, Smart-cards 1 Introduction No cryptographic protocol is stronger than the mechanism protecting its secret keys. However, in many computing and communication systems, there is no "safe place" in which secret keys can be stored and cryptographi...

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