Method CreateSessionCreatedMessage

libi2pd/NTCP2.cpp:239–296

	}

	bool NTCP2Establisher::CreateSessionCreatedMessage (std::mt19937& rng)
	{
		size_t offset = 0;
		// encrypt Y
		i2p::crypto::CBCEncryption encryption;
		encryption.SetKey (i2p::context.GetIdentHash ());
		encryption.Encrypt (GetPub (), 32, m_IV, m_Buffer); // Y
		offset += 32;
		// encryption key for next block (m_K)
		if (!KDF2Bob ()) return false;
		size_t maxPaddingLength = m_IsLongPadding ? NTCP2_SESSION_HANDSHAKE_LONG_MAX_SIZE : NTCP2_SESSION_HANDSHAKE_MAX_SIZE;
		maxPaddingLength -= 64;
		size_t maxMsgSize = m_MaxMsgSize;
#if OPENSSL_PQ
        if (m_PQKeys)
        {
            size_t cipherTextLen = i2p::crypto::GetMLKEMCipherTextLen (m_CryptoType);
			std::vector<uint8_t> kemCiphertext(cipherTextLen);
			uint8_t sharedSecret[32];
			m_PQKeys->Encaps (kemCiphertext.data (), sharedSecret);
			if (!Encrypt (kemCiphertext.data (), m_Buffer + offset, cipherTextLen))
			{
				LogPrint (eLogWarning, "NTCP2: SessionCreated ML-KEM ciphertext section AEAD encryption failed");
				return false;
			}
			MixHash (m_Buffer + offset, cipherTextLen + 16); // encrypt ML-KEM frame
			MixKey (sharedSecret);
            offset += cipherTextLen + 16;
            maxPaddingLength= offset + 32; // 32 bytes following options block size
			// adjust max msg size because we might send smaller message that we can receive
			maxMsgSize = NTCP2_SESSION_HANDSHAKE_LONG_MAX_SIZE + i2p::crypto::MLKEM1024_KEY_LENGTH + 16;
			if (maxMsgSize > m_MaxMsgSize) maxMsgSize = m_MaxMsgSize;
        }
#endif
		// calculate padding length
		if (offset + 32 + maxPaddingLength > maxMsgSize) maxPaddingLength = maxMsgSize - offset - 32;
		auto paddingLength = maxPaddingLength ? rng () % maxPaddingLength : 0;
		uint8_t options[16];
		memset (options, 0, 16);
		htobe16buf (options + 2, paddingLength); // padLen
		htobe32buf (options + 8, (i2p::util::GetMillisecondsSinceEpoch () + 500)/1000); // tsB, rounded to seconds
		// encrypt options
		if (!Encrypt (options, m_Buffer + offset, 16))
		{
			LogPrint (eLogWarning, "NTCP2: SessionCreated failed to encrypt options");
			return false;
		}
		MixHash (m_Buffer + offset, 32);	// encrypted options
		offset += 32;
        // padding
        if (paddingLength)
        {
            RAND_bytes (m_Buffer + offset, paddingLength);
            MixHash (m_Buffer + offset, paddingLength);
        }
        m_BufferLen = offset + paddingLength;
		return true;
	}