/// <summary> /// Returns a number /// </summary> /// /// <returns>The next pseudo-random index</returns> public int NextIndex() { while (true) { if (_remLen < _C) { BitString M = _bitBuffer.GetTrailing(_remLen); int tmpLen = _C - _remLen; int cThreshold = _callCounter + (tmpLen + _hashLen - 1) / _hashLen; while (_callCounter < cThreshold) { byte[] data = new byte[_Z.Length + 4]; Buffer.BlockCopy(_Z, 0, data, 0, _Z.Length); Buffer.BlockCopy(IntUtils.IntToBytes(_callCounter), 0, data, _Z.Length, 4); byte[] H = _digestEngine.ComputeHash(data); M.AppendBits(H); _callCounter++; _remLen += 8 * _hashLen; } _bitBuffer = M; } // assume c less than 32 int i = _bitBuffer.Pop(_C); _remLen -= _C; if (i < (1 << _C) - ((1 << _C) % _N)) { return(i % _N); } } }
/// <summary> /// Returns a number /// </summary> /// /// <returns>The next pseudo-random index</returns> public int NextIndex() { while (true) { if (m_remLen < m_C) { BitString M = m_bitBuffer.GetTrailing(m_remLen); int tmpLen = m_C - m_remLen; int cThreshold = m_callCounter + (tmpLen + m_hashLen - 1) / m_hashLen; while (m_callCounter < cThreshold) { byte[] data = new byte[m_Z.Length + 4]; Buffer.BlockCopy(m_Z, 0, data, 0, m_Z.Length); Buffer.BlockCopy(IntUtils.IntToBytes(m_callCounter), 0, data, m_Z.Length, 4); byte[] H = m_digestEngine.ComputeHash(data); M.AppendBits(H); m_callCounter++; m_remLen += 8 * m_hashLen; } m_bitBuffer = M; } // assume c less than 32 int i = m_bitBuffer.Pop(m_C); m_remLen -= m_C; if (i < (1 << m_C) - ((1 << m_C) % m_N)) { return(i % m_N); } } }
/// <summary> /// Constructs a new index generator /// </summary> /// /// <param name="Seed">A seed of arbitrary length to initialize the index generator</param> /// <param name="EncParam">NtruEncrypt parameters</param> public IndexGenerator(byte[] Seed, NTRUParameters EncParam) { _N = EncParam.N; _C = EncParam.CBits; int minCallsR = EncParam.MinIGFHashCalls; _digestEngine = GetDigest(EncParam.Digest); _hashLen = _digestEngine.DigestSize; _Z = Seed; _callCounter = 0; _bitBuffer = new BitString(); while (_callCounter < minCallsR) { byte[] data = new byte[_Z.Length + 4]; Buffer.BlockCopy(_Z, 0, data, 0, _Z.Length); Buffer.BlockCopy(IntUtils.IntToBytes(_callCounter), 0, data, _Z.Length, 4); byte[] H = _digestEngine.ComputeHash(data); _bitBuffer.AppendBits(H); _callCounter++; } _remLen = minCallsR * 8 * _hashLen; }
/// <summary> /// Constructs a new index generator /// </summary> /// /// <param name="Seed">A seed of arbitrary length to initialize the index generator</param> /// <param name="EncParam">NtruEncrypt parameters</param> public IndexGenerator(byte[] Seed, NTRUParameters EncParam) { _N = EncParam.N; _C = EncParam.CBits; int minCallsR = EncParam.MinIGFHashCalls; _digestEngine = GetDigest(EncParam.Digest); _hashLen = _digestEngine.DigestSize; _Z = Seed; _callCounter = 0; _bitBuffer = new BitString(); while (_callCounter < minCallsR) { byte[] data = new byte[_Z.Length + 4]; Buffer.BlockCopy(_Z, 0, data, 0, _Z.Length); Buffer.BlockCopy(IntUtils.IntToBytes(_callCounter), 0, data, _Z.Length, 4); byte[] H = _digestEngine.ComputeHash(data); _bitBuffer.AppendBits(H); _callCounter++; } _remLen = minCallsR * 8 * _hashLen; }