Divertible Protocols and Atomic Proxy Cryptography

Abstract. First, we introduce the notion of divertibility as a protocol property as opposed to the existing notion as a language property (see Okamoto, Ohta [OO90]). We give a definition of protocol divertibility that applies to arbitrary 2-party protocols and is compatible with Okamoto and Ohta's definition in the case of interactive zero-knowledge proofs. Other important examples falling under the new definition are blind signature protocols. We propose a sufficiency criterion for divertibility that is satisfied by many existing protocols and which, surprisingly, generalizes to cover several protocols not normally associated with divertibility (e.g., Diffie-Hellman key exchange). Next, we introduce atomic proxy cryptography, in which an atomic proxy function, in conjunction with a public proxy key, converts ciphertexts (messages or signatures) for one key into ciphertexts for another. Proxy keys, once generated, may be made public and proxy functions applied in untrusted environ...

• Type: Conference
• Year: 1998
• Where: EUROCRYPT
• Authors: Matt Blaze, Gerrit Bleumer, Martin Strauss
• Keywords: Atomic Proxy Functions, Cryptology, EUROCRYPT 1998, Proxy Cryptography, Proxy Keys