/// <summary>
/// Tests if the key pair is valid.
/// <para>See IEEE 1363.1 section 9.2.4.1.</para>
/// </summary>
///
/// <returns>if the key pair is valid, <c>true</c> otherwise false</returns>
public bool IsValid()
{
int N = ((NTRUPrivateKey)PrivateKey).N;
int q = ((NTRUPrivateKey)PrivateKey).Q;
TernaryPolynomialType polyType = ((NTRUPrivateKey)PrivateKey).PolyType;
if (((NTRUPublicKey)PublicKey).N != N)
{
return(false);
}
if (((NTRUPublicKey)PublicKey).Q != q)
{
return(false);
}
if (((NTRUPrivateKey)PrivateKey).T.ToIntegerPolynomial().Coeffs.Length != N)
{
return(false);
}
IntegerPolynomial h = ((NTRUPublicKey)PublicKey).H.ToIntegerPolynomial();
if (h.Coeffs.Length != N)
{
return(false);
}
if (!h.IsReduced(q))
{
return(false);
}
IntegerPolynomial f = ((NTRUPrivateKey)PrivateKey).T.ToIntegerPolynomial();
if (polyType == TernaryPolynomialType.SIMPLE && !f.IsTernary())
{
return(false);
}
// if t is a ProductFormPolynomial, ternarity of f1,f2,f3 doesn't need to be verified
if (polyType == TernaryPolynomialType.PRODUCT && !(((NTRUPrivateKey)PrivateKey).T.GetType().Equals(typeof(ProductFormPolynomial))))
{
return(false);
}
if (polyType == TernaryPolynomialType.PRODUCT)
{
f.Multiply(3);
f.Coeffs[0] += 1;
f.ModPositive(q);
}
// the key generator pre-multiplies h by 3, so divide by 9 instead of 3
int inv9 = IntEuclidean.Calculate(9, q).X; // 9^-1 mod q
IntegerPolynomial g = f.Multiply(h, q);
g.Multiply(inv9);
g.ModCenter(q);
if (!g.IsTernary())
{
return(false);
}
int dg = N / 3; // see EncryptionParameters.Initialize()
if (g.Count(1) != dg)
{
return(false);
}
if (g.Count(-1) != dg - 1)
{
return(false);
}
return(true);
}
