public AsymmetricCipherKeyPair GenerateKeyPair()
{
int N = Parameters.N;
int q = Parameters.q;
int df = Parameters.df;
int df1 = Parameters.df1;
int df2 = Parameters.df2;
int df3 = Parameters.df3;
int dg = Parameters.dg;
bool fastFp = Parameters.fastFp;
bool sparse = Parameters.sparse;
IPolynomial t;
IntegerPolynomial fq;
IntegerPolynomial fp = null;
// choose a random f that is invertible mod 3 and q
while (true)
{
IntegerPolynomial f;
// choose random t, calculate f and fp
if (fastFp)
{
// if fastFp=true, f is always invertible mod 3
t = Parameters.polyType == (int)NTRUParameters.TERNARY_POLYNOMIAL_TYPE_SIMPLE ? Util.GenerateRandomTernary(N, df, df, sparse, Parameters.Random) : (IPolynomial)ProductFormPolynomial.GenerateRandom(N, df1, df2, df3, df3, Parameters.Random);
f = t.ToIntegerPolynomial();
f.Multiply(3);
f.coeffs[0] += 1;
}
else
{
t = Parameters.polyType == (int)NTRUParameters.TERNARY_POLYNOMIAL_TYPE_SIMPLE ? Util.GenerateRandomTernary(N, df, df - 1, sparse, Parameters.Random) : (IPolynomial)ProductFormPolynomial.GenerateRandom(N, df1, df2, df3, df3 - 1, Parameters.Random);
f = t.ToIntegerPolynomial();
fp = f.InvertF3();
if (fp == null)
{
continue;
}
}
fq = f.InvertFq(q);
if (fq == null)
{
continue;
}
break;
}
// if fastFp=true, fp=1
if (fastFp)
{
fp = new IntegerPolynomial(N);
fp.coeffs[0] = 1;
}
// choose a random g that is invertible mod q
DenseTernaryPolynomial g;
while (true)
{
g = DenseTernaryPolynomial.GenerateRandom(N, dg, dg - 1, Parameters.Random);
if (g.InvertFq(q) != null)
{
break;
}
}
IntegerPolynomial h = g.Multiply(fq, q);
h.Multiply3(q);
h.EnsurePositive(q);
g.Clear();
fq.Clear();
NTRUEncryptionPrivateKeyParameters priv = new NTRUEncryptionPrivateKeyParameters(h, t, fp, Parameters.GetEncryptionParameters());
NTRUEncryptionPublicKeyParameters pub = new NTRUEncryptionPublicKeyParameters(h, Parameters.GetEncryptionParameters());
return(new AsymmetricCipherKeyPair(pub, priv));
}
