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Paper: Key-collisions in (EC)DSA: Attacking Non-repudiation

Authors:
Tomas Rosa
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URL: http://eprint.iacr.org/2002/129
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Abstract: A new kind of attack on the non-repudiation property of digital signature schemes is presented. We introduce a notion of key-collisions, which may allow an attacker to claim that the message (presented to a judge) has been signed by someone else. We show how to compute key-collisions for the DSA and ECDSA signature schemes effectively. The main idea of these attacks has been inspired by the well-known notion of message-collisions, where an attacker claims that the signature presented at the court belongs to a different message. Both of these collision-based attacks significantly weaken the non-repudiation property of signature schemes. Moreover, they weaken the non-repudiation of protocols based on these schemes. It is shown that key-collision resistance of the (EC)DSA schemes requires the incorporation of a mechanism ensuring honest generation of (EC)DSA instances. The usage of such a mechanism shall be verifiable by an independent third party without revealing any secret information. We propose and discuss basic general countermeasures against key-collision attacks on the (EC)DSA schemes.
BibTeX
@misc{eprint-2002-11652,
  title={Key-collisions in (EC)DSA: Attacking Non-repudiation},
  booktitle={IACR Eprint archive},
  keywords={digital signatures, non-repudiation},
  url={http://eprint.iacr.org/2002/129},
  note={Paper supports a talk given at CRYPTO 2002 Rump Session (was: On Key-collisions in (EC)DSA Schemes) t_rosa@volny.cz 12427 received 26 Aug 2002, last revised 10 Jan 2004},
  author={Tomas Rosa},
  year=2002
}