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x/crypto/curve25519,x/crypto/ed25519: reject low order points #31846

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FiloSottile opened this issue May 5, 2019 · 0 comments

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commented May 5, 2019

Rejecting low order points is not strictly necessary, but it helps root out behaviors that can come unexpected to protocol designers (like non-contributory DH, or signature:message:key not being 1:1:1). libsodium already does indiscriminately, and we should too.

https://github.com/jedisct1/libsodium/blob/cec56d867f741e66f78b9fde37d9081643599a2a/src/libsodium/crypto_scalarmult/curve25519/ref10/x25519_ref10.c#L90

This was suggested by Cas Cremers and Dennis Jackson as part of their upcoming work on revisiting small subgroup and invalid curve attacks.

@FiloSottile FiloSottile added the NeedsFix label May 5, 2019

@FiloSottile FiloSottile added this to the Go1.13 milestone May 5, 2019

@FiloSottile FiloSottile self-assigned this May 5, 2019

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