There seems to be a bug in ToBigInteger, that causes the output of
ECFieldElement to sometimes be 33 bits long.
The problem seems to be a leading zero is appended (or left in) during the
conversion. This byte seems to be located in byte[0]. So far it seems that
the value is always zero with these outside-in tests, however further
investigation is warranted.
Then again, if I do have any error in my code, please let me know.
while (true)
{
ECKeyPairGenerator gen = new ECKeyPairGenerator("ECDSA");
Org.BouncyCastle.Asn1.X9.X9ECParameters ecp =
Org.BouncyCastle.Asn1.Sec.SecNamedCurves.GetByName("secp256k1");
ECDomainParameters ecSpec = new ECDomainParameters(ecp.Curve,
ecp.G, ecp.N, ecp.H, ecp.GetSeed());
SecureRandom secureRandom = new SecureRandom();
ECKeyGenerationParameters ecgp = new
ECKeyGenerationParameters(ecSpec, secureRandom);
gen.Init(ecgp);
AsymmetricCipherKeyPair eckp = gen.GenerateKeyPair();
// Cast it
var publicKey = (ECPublicKeyParameters)(eckp.Public);
var privateKey = (ECPrivateKeyParameters)(eckp.Private);
// Get X and Y
var pubxBigInt = publicKey.Q.X.ToBigInteger();
var pubyBigInt = publicKey.Q.Y.ToBigInteger();
// Get Byte Array... whoa, why is the length 33? Can I simply
trim the leading zero?
var pubxBigIntArray = pubyBigInt.ToByteArray();
var pubyBigIntArray = pubyBigInt.ToByteArray();
if (pubyBigIntArray.Length > 32 || pubxBigIntArray.Length > 32)
{
StringBuilder sb = new StringBuilder();
if (pubxBigIntArray.Length > 32)
{
sb.Append(String.Format("X is {0} bits. Bit[0] = {1}",
pubxBigIntArray.Length, pubxBigIntArray[0]));
}
if (pubyBigIntArray.Length > 32)
{
sb.Append(String.Format(" Y is {0} bits. Bit[0] =
{1}",pubyBigIntArray.Length, pubyBigIntArray[0]));
}
Console.WriteLine(sb.ToString());
}
else
{
Console.WriteLine("OK");
}
}
Chris Mankowski
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