[TOM_RUS]

В SC2 было так, но скорее всего сиды уже сменили... Ну и sessionKey тут не вововский помоему, а батлнетовский (64 байта):

using System;
using System.Collections.Generic;
using System.Linq;
using System.Security.Cryptography;
using System.Text;
using WoWSniff.Cryptology;

namespace WoWSniff.BattleNet
{
    public class BNetCrypt
    {
         private static readonly byte[] EncryptServerDataSeed =
        { 0x68, 0xE0, 0xC7, 0x2E, 0xDD, 0xD6, 0xD2, 0xF3,
           0x1E, 0x5A, 0xB1, 0x55, 0xB1, 0x8B, 0x63, 0x1E };

        private static readonly byte[] DecryptClientDataSeed =
        { 0xDE, 0xA9, 0x65, 0xAE, 0x54, 0x3A, 0x1E, 0x93,
           0x9E, 0x69, 0x0C, 0xAA, 0x68, 0xDE, 0x78, 0x39 };

        /// <summary>
        /// Encrypts data sent to the client
        /// </summary>
        private readonly ARC4 _encryptServerData;
        /// <summary>
        /// Decrypts data sent from the client
        /// </summary>
        private readonly ARC4 _decryptClientData;

        public bool EncryptionEnabled { get; set; }

        public byte[] SessionKey { get; set; }

        public BNetCrypt(byte[] sessionKey)
        {
            EncryptionEnabled = false;
            SessionKey = sessionKey;

            var sessionKeyHMAC = new HMACSHA256(sessionKey);
            var encryptHash = sessionKeyHMAC.ComputeHash(EncryptServerDataSeed);
            var decryptHash = sessionKeyHMAC.ComputeHash(DecryptClientDataSeed);

            // Used by the client to decrypt packets sent by the server
            //var decryptServerData = new ARC4(encryptHash); // CLIENT-SIDE

            // Used by the server to decrypt packets sent by the client
            _decryptClientData = new ARC4(decryptHash); // SERVER-SIDE

            // Used by the server to encrypt packets sent to the client
            _encryptServerData = new ARC4(encryptHash); // SERVER-SIDE

            // Used by the client to encrypt packets sent to the server
            //var encryptClientData = new ARC4(decryptHash); // CLIENT-SIDE
        }

        public void Decrypt(byte[] data, int start, int count)
        {
            _decryptClientData.Process(data, start, count);
        }

        public void Encrypt(byte[] data, int start, int count)
        {
            _encryptServerData.Process(data, start, count);
        }
    }
}