Cryptographic Issues Affecting github.com/dedis/kyber package, versions <3.0.13
Snyk CVSS
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Test your applications- Snyk ID SNYK-GOLANG-GITHUBCOMDEDISKYBER-597483
- published 6 Aug 2020
- disclosed 6 Aug 2020
- credit calctopian
How to fix?
Upgrade github.com/dedis/kyber 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.