How to Break Fraud-Detectable Key Recovery.

Copyright [©] (1998) by Association for Computing Machinery, Inc. Permission to make digital or hard copies of part or all of this work for personal or classroom use is granted without fee provided that copies are not made or distrubuted for profit or commericial advantage. To copy otherwise, to republish, to post on servers, or to redistribute to lists, requires prior specific permission and/or a fee.

Fraud detection for software key recovery schemes means that, without knowing the session key, a third party can verify whether the correct session key could be recovered. This concept and a construction by so-called binding data was introduced by Verheul et al. at Eurocrypt '97 to provide for dishonest users that make simple modifications to
messages, e.g., delete the key recovery information, and manipulate the recipient's software such that it decrypts messages even if the key recovery information is incorrect. We show how to break their general construction within their model, in particular without using any other encryption system or any pre-established shared secrets.
We conclude that the concept of binding data does not improve the security of software key recovery but illustrates once more its fundamental problem: it does not improve an authorized third party's ability to eavesdrop on serious criminals.

By: B. Pfitzmann and M. Waidner.

Published in: ACM Operating Systems Review, volume 32, (no 1), pages 23-8 in 1998

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