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Erschienen in:
2005 | OriginalPaper | Buchkapitel
Soundness of Formal Encryption in the Presence of Key-Cycles
verfasst von : Pedro Adão, Gergei Bana, Jonathan Herzog, Andre Scedrov
Erschienen in: Computer Security – ESORICS 2005
Verlag: Springer Berlin Heidelberg
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Both the formal and the computational models of cryptography contain the notion of message
equivalence
or
indistinguishability
. An encryption scheme provides
soundness
for indistinguishability if, when mapping formal messages into the computational model, equivalent formal messages are mapped to indistinguishable computational distributions. Previous soundness results are limited in that they do not apply when
key-cycles
are present. We demonstrate that an encryption scheme provides soundness in the presence of key-cycles if it satisfies the recently-introduced notion of
key-dependent message
(KDM) security. We also show that soundness in the presence of key-cycles (and KDM security) neither implies nor is implied by security against chosen ciphertext attack (CCA-2). Therefore, soundness for key-cycles is possible using a new notion of computational security, not possible using previous such notions, and the relationship between the formal and computational models extends beyond chosen-ciphertext security.