[conformal/btcec] b19d0a: Enforce low S values, by negating the value (modul...

[Yurii Rashkovskii]

  Branch: refs/heads/master
  Home:   https://github.com/conformal/btcec
  Commit: b19d0a0232bf07223bc2384cd1760eb916075077
      
https://github.com/conformal/btcec/commit/b19d0a0232bf07223bc2384cd1760eb916075077
  Author: Yurii Rashkovskii <yra...@gmail.com>
  Date:   2014-07-31 (Thu, 31 Jul 2014)

  Changed paths:
    M signature.go
    M signature_test.go

  Log Message:
  -----------
  Enforce low S values, by negating the value (modulo the order) if above 
order/2.

Reference implementation: 
https://github.com/bitcoin/bitcoin/blob/b7bba43a14a641b6b64bbf48357b2987c1b05800/src/key.cpp#L235-L238

ht @oleganza