public static bool VerificarFirmaElectronica(Punto publicKey, byte[] message, byte[] signature)
{
var parsed = ASN1_Generator.ASN1_Generator.Parse(signature);
var r = ((ASN1_Integer)((ASN1_Sequence)parsed
.Elements[0])
.content[0])
.Value;
var s = ((ASN1_Integer)((ASN1_Sequence)parsed
.Elements[0])
.content[1])
.Value;
if (!(0 < r && r < Params.n))
{
return(false);
}
if (!(0 < s && s < Params.n))
{
return(false);
}
var eHash = FirmaElectronica.ObtenerHash(message);
var e = new BigInteger(eHash);
if (e.Sign == -1)
{
e = BigInteger.Negate(e);
}
var w = Arithmetic.Inversion_ExtendedEuclidean(s, Params.n);
var u1 = Arithmetic.Mod(e * w, Params.n);
var u2 = Arithmetic.Mod(r * w, Params.n);
var X = u1 * Params.G + u2 * publicKey;
if (X.EsInfinito || X.EsCero)
{
return(false);
}
var v = Arithmetic.Mod(X.x, Params.n);
if (v == r)
{
return(true);
}
else
{
return(false);
}
}
public static byte[] GenerarFirmaElectronica(byte[] message, BigInteger privateKey)
{
while (true)
{
//Genero un valor 'k' aleatorio
BigInteger k = Helper.Random(Params.n);
//Calculo el punto P = k*G
Punto kP = k * Params.G;
BigInteger r = Arithmetic.Mod(kP.x, Params.n);
if (r.IsZero)
{
continue;
}
var eHash = FirmaElectronica.ObtenerHash(message);
var e = new BigInteger(eHash);
if (e.Sign == -1)
{
e = BigInteger.Negate(e);
}
BigInteger s = Arithmetic.Mod(
Arithmetic.Inversion_ExtendedEuclidean(k, Params.n) * (e + privateKey * r), Params.n
);
var asn1 = new ASN1_Generator.ASN1_Generator();
var seq = new ASN1_Generator.ASN1_Sequence();
seq.content.Add(new ASN1_Generator.ASN1_Integer()
{
Value = r
});
seq.content.Add(new ASN1_Generator.ASN1_Integer()
{
Value = s
});
asn1.Elements.Add(seq);
return(asn1.GetBytes());
}
}