Comments on certain past cryptographic flaws affecting fully encrypted censorship circumvention protocols

ePrint Report: Comments on certain past cryptographic flaws affecting fully encrypted censorship circumvention protocols

David Fifield

This article presents three retrospective case studies of cryptography-related flaws in censorship circumvention protocols: a decryption oracle in Shadowsocks “stream cipher” methods, non-uniform Elligator public key representatives in obfs4, and a replay-based active distinguishing attack exploiting malleability in VMess. These three protocols come from the family of “fully encrypted” circumvention protocols: their traffic in both directions is indistinguishable from a uniformly random stream of …

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