[Resource Topic] 2012/497: The low-call diet: Authenticated Encryption for call counting HSM users

Welcome to the resource topic for 2012/497

Title:
The low-call diet: Authenticated Encryption for call counting HSM users

Authors: Mike Bond, George French, Nigel P. Smart, Gaven J. Watson

Abstract:

We present a new mode of operation for obtaining authenticated encryption suited for use in banking and government environments where cryptographic services are only available via a Hardware Security Module (HSM) which protects the keys but offers a limited API. The practical problem is that despite the existence of better modes of operation, modern HSMs still provide nothing but a basic (unauthenticated) CBC mode of encryption, and since they mediate all access to the key, solutions must work around this. Our mode of operation makes only a single call to the HSM, yet provides a secure authenticated encryption scheme; authentication is obtained by manipulation of the plaintext being passed to the HSM via a call to an unkeyed hash function. The scheme offers a considerable performance improvement compared to more traditional authenticated encryption techniques which must be implemented using multiple calls to the HSM. Our new mode of operation is provided with a proof of security, on the assumption that the underlying block cipher used in the CBC mode is a strong pseudorandom permutation, and that the hash function is modelled as a random oracle.

ePrint: https://eprint.iacr.org/2012/497

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