Dotnet/Ed25519
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Added extension for determine public key

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This commit is contained in:
Thorsten Sommer 2020-01-03 20:25:34 +01:00
parent 6c6a50c395
commit 9278224f44
1 changed files with 17 additions and 0 deletions
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17
Ed25519/Extensions.cs
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@ -103,5 +103,22 @@ namespace Ed25519
{
return data[index / 8] >> (index % 8) & 1;
}
public static ReadOnlySpan<byte> ExtractPublicKey(this ReadOnlySpan<byte> privateKey)
{
var hash = privateKey.ComputeHash();
var a = Constants.TWO_POW_BIT_LENGTH_MINUS_TWO;
for (var i = 3; i < Constants.BIT_LENGTH - 2; i++)
{
var bit = hash.GetBit(i);
if (bit != 0)
{
a += Constants.TWO_POW_CACHE[i];
}
}
var bigA = Constants.B.ScalarMul(a);
return bigA.EncodePoint();
}
}
}