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I'm doing summer cryptography research and I am have been looking for a security analysis of the Guillou-Quisquater (GQ) digital signature scheme, but I have been unable to find one.

Since this is not a very common digital signature scheme I will mention the protocol.

GQ: Public: $n,e,I$ has function $H$, where $I \equiv S^{e} \mod n$

Private: $s$

Signature: $(x,y)$ where $x \equiv r^{e} \mod n, c=h(m,x)$, and $y \equiv rS^{c} \mod n$

To verify: Check that $y^{e} \equiv x I^{h(m,x)} \mod n$ (this works because $y^{e} \equiv (rS^{c})^{e} \equiv r^{e}S^{ce} \equiv xI^{c}$)

Any references to papers in which this could be found would be very helpful. Thank you!

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  • $\begingroup$ I think your notation is inconsistent. Also, see the following: scholar.google.com/… $\endgroup$
    – Steve Huntsman
    Commented Jul 17, 2012 at 21:16
  • $\begingroup$ @Steve Huntsman: Care to extrapolate upon your comment about the inconsistency of my notation? $\endgroup$
    – Samuel Reid
    Commented Jul 18, 2012 at 7:30

1 Answer 1

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M. Bellare, A. Palacio - GQ and Schnorr Identification Schemes: Proofs of Security against Impersonation under Active and Concurrent Attacks

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