GCNet is a Grand Chase Season Eternal networking library created by SyntaxDev which provides cryptography and packet-related features.
The CryptoLib assembly provides some core features like packet encryption and decryption, HMAC packet hashing, key generation and cryptography constants.
The PacketLib assembly gives an I/O packet managing by providing compression, data reading and writing in addition to the own cryptography functions.
To build the project, you should use Visual Studio 2015 with .NET Framework 4.5.2. For those who wish, here is the latest precompiled binary.