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using System;
using Org.BouncyCastle.Crypto.Parameters;
using Org.BouncyCastle.Math;
using Org.BouncyCastle.Math.EC.Multiplier;
using Org.BouncyCastle.Security;
using Org.BouncyCastle.Utilities;
namespace Org.BouncyCastle.Crypto.Generators
{
class DHKeyGeneratorHelper
{
internal static readonly DHKeyGeneratorHelper Instance = new DHKeyGeneratorHelper();
private DHKeyGeneratorHelper()
{
}
internal BigInteger CalculatePrivate(
DHParameters dhParams,
SecureRandom random)
{
int limit = dhParams.L;
if (limit != 0)
{
int minWeight = limit >> 2;
for (;;)
{
BigInteger x = new BigInteger(limit, random).SetBit(limit - 1);
if (WNafUtilities.GetNafWeight(x) >= minWeight)
{
return x;
}
}
}
BigInteger min = BigInteger.Two;
int m = dhParams.M;
if (m != 0)
{
min = BigInteger.One.ShiftLeft(m - 1);
}
BigInteger q = dhParams.Q;
if (q == null)
{
q = dhParams.P;
}
BigInteger max = q.Subtract(BigInteger.Two);
{
int minWeight = max.BitLength >> 2;
for (;;)
{
BigInteger x = BigIntegers.CreateRandomInRange(min, max, random);
if (WNafUtilities.GetNafWeight(x) >= minWeight)
{
return x;
}
}
}
}
internal BigInteger CalculatePublic(
DHParameters dhParams,
BigInteger x)
{
return dhParams.G.ModPow(x, dhParams.P);
}
}
}
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