Cryptographic Issues Affecting go.dedis.ch/kyber/v3 package, versions <3.0.13


0.0
medium
  • Attack Complexity

    High

  • Availability

    High

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  • snyk-id

    SNYK-GOLANG-GODEDISCHKYBERV3-1083973

  • published

    6 Aug 2020

  • disclosed

    6 Aug 2020

  • credit

    calctopian

How to fix?

Upgrade go.dedis.ch/kyber/v3 to version 3.0.13 or higher.

Overview

Affected versions of this package are vulnerable to Cryptographic Issues. If a malicious attacker adds one of points of the subgroups of small order (i.e., non-identity torsion points) to a key image, up to 7 double spends could be performed for each authentic spend on the cothority: this is now prevented by the Ge25519HasSmallOrder function.

This happens because multiplying the sum of a torsion point by a multiple of 8 and a "normal" point will return the same point, because multiplying small subgroup points by 8 returns the identity element. Without the function Ge25519HasSmallOrder, signatures verify on malicious key images derived from the authentic ones.

References