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LibTMCG 1.3.17 released

Item posted by Heiko Stamer <stamer> on Wed 23 Jan 2019 08:34:06 PM UTC.

This is a maintenance release that fixes a major bug in the VSSHE module (Groth's shuffle protocol). The verification of the special component E_d with respect to membership in the underlying commitment group has been done wrongly by a fast exponentiation function with fixed bases. Hence the check of membership for this component is always bypassed and thus a malicious prover may disturb the shuffle process by supplying a bad value. However, it is extremely difficult to bypass the other checks, if E_d is tampered (e.g. set to zero). Please note that the vulnerability has only an impact on the optimized shuffle interfaces (e.g. TMCG_VerifyStackEquality_Groth) of LibTMCG. Moreover, some other minor improvements are included in this release.

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