Packet encryption/decryption function

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Good day to you all!
I have a quick question for the pro-coders around here:
I have a function to encrypt/decrypt my packets in my online game using defined keys.4
Here are the keys, generated random:

C++

BYTE server_keys[2][256] = {
	{
		0xFC, 0x77, 0xA1, 0x85, 0x1F, 0x30, 0x51, 0x20, 0x93, 0x4A, 0xE3, 0x10, 0x0E, 0x32, 0x58,
			0x64, 0x36, 0x8C, 0x19, 0xF0, 0x61, 0xE0, 0xDF, 0x9E, 0x9F, 0x90, 0xD0, 0x05, 0xFA, 0xEB,
			0x3D, 0x4B, 0xA5, 0xF1, 0x72, 0x73, 0xD4, 0xB5, 0x70, 0xD7, 0xCD, 0x9A, 0x95, 0x2B, 0xC9,
			0x00, 0x8E, 0xAC, 0x35, 0x1B, 0xE7, 0x7B, 0xC3, 0x15, 0x11, 0xF6, 0xAD, 0x5B, 0x87, 0x86,
			0xB4, 0x9B, 0x26, 0xDB, 0xDE, 0x1C, 0x66, 0x24, 0xD8, 0x27, 0x6A, 0xBD, 0x5D, 0x8D, 0x7D,
			0x0D, 0xAE, 0x8B, 0xA9, 0x62, 0x6B, 0x0B, 0xE2, 0x5C, 0x6C, 0xBE, 0x54, 0x55, 0x6E, 0xBF,
			0x3F, 0x88, 0x99, 0xB0, 0x48, 0x16, 0x5A, 0x34, 0xA6, 0xE8, 0xFD, 0xD3, 0xE4, 0x82, 0xD6,
			0x8A, 0x3B, 0xFE, 0xA4, 0x94, 0xF8, 0x06, 0x97, 0xCB, 0xF5, 0x33, 0x79, 0xD9, 0x83, 0x4F,
			0xB1, 0xAB, 0xA2, 0x69, 0x91, 0xFF, 0xC6, 0x2C, 0x68, 0xC1, 0xAA, 0xC4, 0x1D, 0x18, 0x3A,
			0xBC, 0x04, 0x2F, 0xA3, 0xFB, 0x17, 0x89, 0x25, 0x02, 0xCF, 0xDD, 0x2D, 0x6D, 0xC5, 0xC2,
			0x46, 0x01, 0xE5, 0xED, 0x2E, 0xDA, 0x31, 0x37, 0x40, 0xC8, 0xB6, 0xE9, 0x7C, 0x45, 0xF3,
			0x47, 0x22, 0xF9, 0x63, 0xB9, 0x13, 0x38, 0x78, 0x2A, 0xC0, 0xEC, 0xEF, 0x28, 0x12, 0x6F,
			0x75, 0xEA, 0x29, 0x84, 0x9C, 0x44, 0x96, 0x0A, 0x59, 0x76, 0x92, 0x41, 0xF2, 0x67, 0x08,
			0xB8, 0x43, 0xCA, 0x1E, 0xE1, 0x52, 0x3C, 0x42, 0xEE, 0xA8, 0x5F, 0x23, 0x1A, 0xD5, 0x7F,
			0xC7, 0x5E, 0x50, 0x81, 0xF7, 0x7A, 0x65, 0x09, 0xCC, 0x60, 0x0F, 0x9D, 0x53, 0x80, 0xA0,
			0x98, 0xB3, 0xA7, 0x49, 0x57, 0x7E, 0x3E, 0x03, 0xDC, 0x39, 0xBB, 0x8F, 0xCE, 0x4E, 0xF4,
			0xE6, 0xB2, 0x74, 0x21, 0x0C, 0x71, 0x07, 0xB7, 0xAF, 0x56, 0x14, 0x4D, 0xD2, 0x4C, 0xD1,
			0xBA
	}, {
		0xEC, 0x48, 0x4E, 0x18, 0x93, 0x4C, 0x98, 0x7F, 0xDA, 0x43, 0x89, 0x6A, 0x1E, 0xAA, 0xF9,
			0x65, 0x07, 0x22, 0xD8, 0x52, 0x01, 0xCA, 0x61, 0x7A, 0x85, 0x91, 0x54, 0x08, 0xE6, 0x8D,
			0x41, 0xDD, 0xD1, 0xC8, 0x72, 0x31, 0x94, 0xFB, 0xC7, 0x4F, 0xE7, 0x9C, 0x3E, 0x46, 0xD5,
			0xE4, 0x76, 0xAE, 0xAB, 0x77, 0xBF, 0x11, 0x09, 0x51, 0xD7, 0x55, 0x39, 0x45, 0xA4, 0xFE,
			0xBA, 0x9A, 0x6E, 0xB8, 0x2C, 0x57, 0x32, 0x2A, 0x5F, 0x50, 0xD4, 0x5B, 0xB3, 0x3A, 0xA6,
			0x9B, 0x3C, 0x14, 0xDC, 0x1D, 0xFC, 0x27, 0x6C, 0x86, 0x17, 0x5A, 0x5C, 0xDB, 0x78, 0x75,
			0x70, 0xF7, 0x3D, 0x8E, 0xE1, 0x05, 0x0D, 0xF3, 0x20, 0x6F, 0x8C, 0x36, 0x7C, 0x69, 0x06,
			0xA3, 0x7D, 0xCF, 0xE3, 0x3B, 0x67, 0x40, 0xF8, 0xFA, 0xA2, 0x0C, 0xB6, 0xAD, 0xC6, 0xA0,
			0xBE, 0xA1, 0x37, 0xB0, 0xB2, 0x12, 0x9E, 0x23, 0xD9, 0xD0, 0xCD, 0x4B, 0x84, 0x1C, 0xD6,
			0xED, 0xE8, 0xC1, 0x3F, 0x2F, 0xB5, 0x38, 0x8A, 0x71, 0xF2, 0x28, 0xC3, 0xD2, 0x6D, 0xB9,
			0x30, 0xA9, 0x73, 0xA5, 0x02, 0x5D, 0xC9, 0x10, 0x62, 0xFD, 0x47, 0xAF, 0x81, 0x2B, 0x9D,
			0xC0, 0x90, 0x99, 0x74, 0x49, 0x44, 0xB4, 0x8F, 0x92, 0x0E, 0xB1, 0xE0, 0x0B, 0x0A, 0x7E,
			0x95, 0x96, 0x34, 0x68, 0x53, 0xCB, 0xEF, 0xCC, 0x2D, 0x56, 0xEE, 0xF0, 0x24, 0x1B, 0xF5,
			0x66, 0xD3, 0x03, 0x00, 0x15, 0x4A, 0xE2, 0xA7, 0x58, 0x1A, 0xE5, 0x29, 0x63, 0x25, 0xB7,
			0xCE, 0xBB, 0xF4, 0x7B, 0x4D, 0xBD, 0x35, 0x79, 0x0F, 0x80, 0x26, 0xE9, 0xAC, 0xEB, 0x97,
			0x16, 0x82, 0xA8, 0xBC, 0x13, 0x21, 0x19, 0x1F, 0x2E, 0xC2, 0x87, 0x88, 0x9F, 0x83, 0xEA,
			0x59, 0x42, 0xC5, 0x04, 0x5E, 0x60, 0xF6, 0x33, 0xC4, 0xF1, 0x6B, 0x64, 0xDE, 0x8B, 0xDF,
			0xFF
	}
};

BYTE client_keys[2][256] = {
	{
		0xC6, 0x14, 0x9A, 0xC5, 0xF3, 0x5F, 0x68, 0x10, 0x1B, 0x34, 0xB2, 0xB1, 0x73, 0x60, 0xAE,
			0xDA, 0x9D, 0x33, 0x7D, 0xE5, 0x4D, 0xC7, 0xE1, 0x54, 0x03, 0xE7, 0xCC, 0xC1, 0x85, 0x4F,
			0x0C, 0xE8, 0x62, 0xE6, 0x11, 0x7F, 0xC0, 0xD0, 0xDC, 0x51, 0x91, 0xCE, 0x43, 0xA3, 0x40,
			0xBC, 0xE9, 0x8B, 0x96, 0x23, 0x42, 0xF7, 0xB6, 0xD8, 0x65, 0x7A, 0x8D, 0x38, 0x49, 0x6D,
			0x4C, 0x5C, 0x2A, 0x8A, 0x6F, 0x1E, 0xF1, 0x09, 0xAA, 0x39, 0x2B, 0xA0, 0x01, 0xA9, 0xC8,
			0x83, 0x05, 0xD6, 0x02, 0x27, 0x45, 0x35, 0x13, 0xB8, 0x1A, 0x37, 0xBD, 0x41, 0xCB, 0xF0,
			0x55, 0x47, 0x56, 0x9B, 0xF4, 0x44, 0xF5, 0x16, 0x9E, 0xCF, 0xFB, 0x0F, 0xC3, 0x6E, 0xB7,
			0x67, 0x0B, 0xFA, 0x52, 0x94, 0x3E, 0x63, 0x5A, 0x8F, 0x22, 0x98, 0xA8, 0x59, 0x2E, 0x31,
			0x58, 0xD9, 0x17, 0xD5, 0x66, 0x6A, 0xB3, 0x07, 0xDB, 0xA2, 0xE2, 0xEE, 0x84, 0x18, 0x53,
			0xEB, 0xEC, 0x0A, 0x8E, 0xFD, 0x64, 0x1D, 0x5D, 0xAC, 0xA6, 0x19, 0xAD, 0x04, 0x24, 0xB4,
			0xB5, 0xE0, 0x06, 0xA7, 0x3D, 0x4B, 0x29, 0xA4, 0x7E, 0xED, 0x77, 0x79, 0x72, 0x69, 0x3A,
			0x99, 0x4A, 0xCA, 0xE3, 0x97, 0x0D, 0x30, 0xDE, 0x75, 0x2F, 0xA1, 0x7B, 0xAF, 0x7C, 0x48,
			0xAB, 0x8C, 0x74, 0xD1, 0x3F, 0x95, 0x3C, 0xD3, 0xE4, 0xD7, 0x78, 0x32, 0xA5, 0x89, 0xEA,
			0x92, 0xF8, 0xF2, 0x76, 0x26, 0x21, 0x9C, 0x15, 0xB9, 0xBB, 0x82, 0xD2, 0x6B, 0x81, 0x20,
			0x93, 0xC4, 0x46, 0x2C, 0x86, 0x36, 0x12, 0x80, 0x08, 0x57, 0x4E, 0x1F, 0xFC, 0xFE, 0xB0,
			0x5E, 0xC9, 0x6C, 0x2D, 0xCD, 0x1C, 0x28, 0x88, 0xDD, 0xEF, 0xDF, 0x00, 0x87, 0xBE, 0xBA,
			0xBF, 0xF9, 0x90, 0x61, 0xD4, 0xC2, 0xF6, 0x5B, 0x70, 0x0E, 0x71, 0x25, 0x50, 0x9F, 0x3B,
			0xFF
	}, {
		0x2D, 0x97, 0x8F, 0xE8, 0x88, 0x1B, 0x6F, 0xF6, 0xC2, 0xD9, 0xBB, 0x51, 0xF4, 0x4B, 0x0C,
			0xDC, 0x0B, 0x36, 0xB2, 0xAA, 0xFA, 0x35, 0x5F, 0x8C, 0x85, 0x12, 0xCF, 0x31, 0x41, 0x84,
			0xC6, 0x04, 0x07, 0xF3, 0xA6, 0xCE, 0x43, 0x8E, 0x3E, 0x45, 0xB1, 0xB6, 0xAD, 0x2B, 0x7F,
			0x92, 0x9A, 0x89, 0x05, 0x9C, 0x0D, 0x73, 0x61, 0x30, 0x10, 0x9D, 0xAB, 0xEA, 0x86, 0x6A,
			0xC9, 0x1E, 0xE7, 0x5A, 0x9E, 0xBF, 0xCA, 0xC4, 0xB9, 0xA3, 0x96, 0xA5, 0x5E, 0xE4, 0x09,
			0x1F, 0xFD, 0xFB, 0xEE, 0x77, 0xD4, 0x06, 0xC8, 0xDE, 0x56, 0x57, 0xF9, 0xE5, 0x0E, 0xBC,
			0x60, 0x39, 0x53, 0x48, 0xD3, 0xCD, 0xDB, 0x14, 0x4F, 0xA8, 0x0F, 0xD8, 0x42, 0xC1, 0x80,
			0x7B, 0x46, 0x50, 0x54, 0x93, 0x58, 0xB3, 0x26, 0xF5, 0x22, 0x23, 0xF2, 0xB4, 0xBD, 0x01,
			0xAC, 0x74, 0xD7, 0x33, 0xA2, 0x4A, 0xE6, 0xD1, 0xDF, 0xD5, 0x67, 0x76, 0xB7, 0x03, 0x3B,
			0x3A, 0x5B, 0x8D, 0x69, 0x4D, 0x11, 0x49, 0x2E, 0xEC, 0x19, 0x7C, 0xBE, 0x08, 0x6D, 0x2A,
			0xBA, 0x70, 0xE1, 0x5C, 0x29, 0x3D, 0xB8, 0xDD, 0x17, 0x18, 0xE0, 0x02, 0x7A, 0x8A, 0x6C,
			0x20, 0x62, 0xE3, 0xCC, 0x4E, 0x82, 0x79, 0x2F, 0x38, 0x4C, 0xF8, 0x5D, 0x78, 0xF1, 0xE2,
			0x3C, 0x25, 0xA0, 0xF7, 0xC3, 0xA9, 0xFF, 0xEB, 0x87, 0x47, 0x55, 0x59, 0xAE, 0x81, 0x95,
			0x34, 0x83, 0x94, 0x7E, 0xD2, 0x9F, 0x2C, 0xC5, 0x71, 0xDA, 0x28, 0xED, 0x90, 0x1A, 0xFE,
			0xFC, 0x65, 0x24, 0xD0, 0x68, 0x27, 0x44, 0x75, 0x9B, 0x3F, 0xE9, 0x91, 0x40, 0x16, 0x15,
			0xC7, 0x52, 0x0A, 0x66, 0x98, 0xF0, 0x32, 0x63, 0xA1, 0xB5, 0x1D, 0xAF, 0x99, 0xCB, 0xB0,
			0x13, 0x21, 0xC0, 0xA4, 0xEF, 0x72, 0x37, 0xD6, 0x6E, 0xA7, 0x1C, 0x8B, 0x00, 0x64, 0x6B,
			0x7D
	}
};

here is the function:

C++

typedef enum PROCESS_TYPE
{
	ENCRYPT = 0,
	DECRYPT = 1
};

inline void process_data(const PROCESS_TYPE type, const BYTE(*keys)[KEYS_NUMBER], BYTE * pData, const unsigned int uLen)
{

	for (unsigned int i = 0; i < uLen; ++i)
	{
		pData[i] = keys[type][pData[i]];
	}
}

So i hooked on client site send() and i am trying to send encrypted packets like this:

C++

process_data(ENCRYPT, client_keys, (BYTE *) buf, len);

And on server side i hooked recv() and i am trying to decrypt like this:

C++

process_data(DECRYPT, server_keys, (BYTE *) buf, size);

The problem? Well it always gives me socket header error... so when trying to DECRYPT the packet it wont work... i cannot understand why, some help please?

Posted 27-Feb-15 21:07pm

User 9994025

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Comments

Richard MacCutchan 28-Feb-15 4:40am

Well it always gives me socket header error.
Where?

[no name] 28-Feb-15 7:16am

In the gameserver, recvdataparse trows that error. It is a muonline server

enhzflep 28-Feb-15 4:45am

Are you trying to encrypt the entire packet, or just the payload it contains?

I think you'll find nothing but disappointment if trying to encrypt the packet's header as well as the payload.

enhzflep 28-Feb-15 7:32am

Even if one looks at a UDP packet, it must have a header. The format of this header is pre-defined and is used by network layers lower than the one your program runs in. (Refer: OSI model - OSI model )
I.e - the data in the header is used before you get a chance to look at the packet. So, if you send an invalid (encrypted) header, the receiving end can't do anything with it.

Perhaps I'm misunderstanding what/how you're doing and some more explanation and code from you would help.

Richard MacCutchan 28-Feb-15 11:58am

There is a lesson to be learned there.

Richard MacCutchan 1-Mar-15 3:18am

The lesson is, do not copy code from the internet unless you are sure that you understand what it is doing. And if it does not work then the only person who can really help you is the one who wrote it.

Richard MacCutchan 1-Mar-15 3:59am

The issue is exactly the same, it is someone else's code so he is the one who will know why it does not work. And a "good developer" would be happy to help you.

Richard MacCutchan 1-Mar-15 3:16am

Unfortunately, that does not tell us anything useful that would help us to help you. Remember, we cannot see your screen, read your hard disk, or guess what your code may be doing.

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enhzflep · Accepted Answer · 2015-02-28T20:52:00

I think that the problem seems to be in the order of operations you're performing.

In your comment, you state that a successful operation transforms:
0xC1 0x06 0xA9 0x20 0x9C 0x2F

into

0x81 0x6F 0x4E 0x07 0xB8 0x89

In order to make this transformation, I needed to DECRYPT using the client_keys - whereas your question had given me the impression that the first 6 byes were the original, unmodified data to be transmitted.

It then follows that the opposite of DECRYPT using client_keys would be to ENCRYPT using server_keys, so I tried that. Guess what? The data's gone 'full-circle' and is transformed back into the original sequence, 0xC1 0x06 0xA9 0x20 0x9C 0x2F

I tried all of the 4 combinations with an input of 0xC1 0x06 0xA9 0x20 0x9C 0x2F

Method          Output
---------------------------------------------
ENCRYPT client: 0x89 0x68 0x97 0x62 0x29 0x8B
ENCRYPT server: 0x67 0x51 0xB9 0xA5 0x31 0xAC
DECRYPT client: 0x81 0x6F 0x4E 0x07 0xB8 0x89  <--- Here's the expected output.
DECRYPT server: 0x1B 0x98 0x49 0xD1 0xC9 0xAE

The only one that makes the successful transformation that you mention, was DECRYPT client. This lends yet more weight to my belief that you've become confused somehow and applied the wrong transformations at the wrong times.

Anyway, here's a short (as can be!) snippet that changes the data and then changes it back again. Hope it helps. :)

C++

#include <cstdio>

typedef unsigned char BYTE;

BYTE server_keys[2][256] = {
	{
		0xFC, 0x77, 0xA1, 0x85, 0x1F, 0x30, 0x51, 0x20, 0x93, 0x4A, 0xE3, 0x10, 0x0E, 0x32, 0x58,
		0x64, 0x36, 0x8C, 0x19, 0xF0, 0x61, 0xE0, 0xDF, 0x9E, 0x9F, 0x90, 0xD0, 0x05, 0xFA, 0xEB,
		0x3D, 0x4B, 0xA5, 0xF1, 0x72, 0x73, 0xD4, 0xB5, 0x70, 0xD7, 0xCD, 0x9A, 0x95, 0x2B, 0xC9,
		0x00, 0x8E, 0xAC, 0x35, 0x1B, 0xE7, 0x7B, 0xC3, 0x15, 0x11, 0xF6, 0xAD, 0x5B, 0x87, 0x86,
		0xB4, 0x9B, 0x26, 0xDB, 0xDE, 0x1C, 0x66, 0x24, 0xD8, 0x27, 0x6A, 0xBD, 0x5D, 0x8D, 0x7D,
		0x0D, 0xAE, 0x8B, 0xA9, 0x62, 0x6B, 0x0B, 0xE2, 0x5C, 0x6C, 0xBE, 0x54, 0x55, 0x6E, 0xBF,
		0x3F, 0x88, 0x99, 0xB0, 0x48, 0x16, 0x5A, 0x34, 0xA6, 0xE8, 0xFD, 0xD3, 0xE4, 0x82, 0xD6,
		0x8A, 0x3B, 0xFE, 0xA4, 0x94, 0xF8, 0x06, 0x97, 0xCB, 0xF5, 0x33, 0x79, 0xD9, 0x83, 0x4F,
		0xB1, 0xAB, 0xA2, 0x69, 0x91, 0xFF, 0xC6, 0x2C, 0x68, 0xC1, 0xAA, 0xC4, 0x1D, 0x18, 0x3A,
		0xBC, 0x04, 0x2F, 0xA3, 0xFB, 0x17, 0x89, 0x25, 0x02, 0xCF, 0xDD, 0x2D, 0x6D, 0xC5, 0xC2,
		0x46, 0x01, 0xE5, 0xED, 0x2E, 0xDA, 0x31, 0x37, 0x40, 0xC8, 0xB6, 0xE9, 0x7C, 0x45, 0xF3,
		0x47, 0x22, 0xF9, 0x63, 0xB9, 0x13, 0x38, 0x78, 0x2A, 0xC0, 0xEC, 0xEF, 0x28, 0x12, 0x6F,
		0x75, 0xEA, 0x29, 0x84, 0x9C, 0x44, 0x96, 0x0A, 0x59, 0x76, 0x92, 0x41, 0xF2, 0x67, 0x08,
		0xB8, 0x43, 0xCA, 0x1E, 0xE1, 0x52, 0x3C, 0x42, 0xEE, 0xA8, 0x5F, 0x23, 0x1A, 0xD5, 0x7F,
		0xC7, 0x5E, 0x50, 0x81, 0xF7, 0x7A, 0x65, 0x09, 0xCC, 0x60, 0x0F, 0x9D, 0x53, 0x80, 0xA0,
		0x98, 0xB3, 0xA7, 0x49, 0x57, 0x7E, 0x3E, 0x03, 0xDC, 0x39, 0xBB, 0x8F, 0xCE, 0x4E, 0xF4,
		0xE6, 0xB2, 0x74, 0x21, 0x0C, 0x71, 0x07, 0xB7, 0xAF, 0x56, 0x14, 0x4D, 0xD2, 0x4C, 0xD1,
		0xBA
	},
	{
		0xEC, 0x48, 0x4E, 0x18, 0x93, 0x4C, 0x98, 0x7F, 0xDA, 0x43, 0x89, 0x6A, 0x1E, 0xAA, 0xF9,
		0x65, 0x07, 0x22, 0xD8, 0x52, 0x01, 0xCA, 0x61, 0x7A, 0x85, 0x91, 0x54, 0x08, 0xE6, 0x8D,
		0x41, 0xDD, 0xD1, 0xC8, 0x72, 0x31, 0x94, 0xFB, 0xC7, 0x4F, 0xE7, 0x9C, 0x3E, 0x46, 0xD5,
		0xE4, 0x76, 0xAE, 0xAB, 0x77, 0xBF, 0x11, 0x09, 0x51, 0xD7, 0x55, 0x39, 0x45, 0xA4, 0xFE,
		0xBA, 0x9A, 0x6E, 0xB8, 0x2C, 0x57, 0x32, 0x2A, 0x5F, 0x50, 0xD4, 0x5B, 0xB3, 0x3A, 0xA6,
		0x9B, 0x3C, 0x14, 0xDC, 0x1D, 0xFC, 0x27, 0x6C, 0x86, 0x17, 0x5A, 0x5C, 0xDB, 0x78, 0x75,
		0x70, 0xF7, 0x3D, 0x8E, 0xE1, 0x05, 0x0D, 0xF3, 0x20, 0x6F, 0x8C, 0x36, 0x7C, 0x69, 0x06,
		0xA3, 0x7D, 0xCF, 0xE3, 0x3B, 0x67, 0x40, 0xF8, 0xFA, 0xA2, 0x0C, 0xB6, 0xAD, 0xC6, 0xA0,
		0xBE, 0xA1, 0x37, 0xB0, 0xB2, 0x12, 0x9E, 0x23, 0xD9, 0xD0, 0xCD, 0x4B, 0x84, 0x1C, 0xD6,
		0xED, 0xE8, 0xC1, 0x3F, 0x2F, 0xB5, 0x38, 0x8A, 0x71, 0xF2, 0x28, 0xC3, 0xD2, 0x6D, 0xB9,
		0x30, 0xA9, 0x73, 0xA5, 0x02, 0x5D, 0xC9, 0x10, 0x62, 0xFD, 0x47, 0xAF, 0x81, 0x2B, 0x9D,
		0xC0, 0x90, 0x99, 0x74, 0x49, 0x44, 0xB4, 0x8F, 0x92, 0x0E, 0xB1, 0xE0, 0x0B, 0x0A, 0x7E,
		0x95, 0x96, 0x34, 0x68, 0x53, 0xCB, 0xEF, 0xCC, 0x2D, 0x56, 0xEE, 0xF0, 0x24, 0x1B, 0xF5,
		0x66, 0xD3, 0x03, 0x00, 0x15, 0x4A, 0xE2, 0xA7, 0x58, 0x1A, 0xE5, 0x29, 0x63, 0x25, 0xB7,
		0xCE, 0xBB, 0xF4, 0x7B, 0x4D, 0xBD, 0x35, 0x79, 0x0F, 0x80, 0x26, 0xE9, 0xAC, 0xEB, 0x97,
		0x16, 0x82, 0xA8, 0xBC, 0x13, 0x21, 0x19, 0x1F, 0x2E, 0xC2, 0x87, 0x88, 0x9F, 0x83, 0xEA,
		0x59, 0x42, 0xC5, 0x04, 0x5E, 0x60, 0xF6, 0x33, 0xC4, 0xF1, 0x6B, 0x64, 0xDE, 0x8B, 0xDF,
		0xFF
	}
};

BYTE client_keys[2][256] = {
	{
		0xC6, 0x14, 0x9A, 0xC5, 0xF3, 0x5F, 0x68, 0x10, 0x1B, 0x34, 0xB2, 0xB1, 0x73, 0x60, 0xAE,
		0xDA, 0x9D, 0x33, 0x7D, 0xE5, 0x4D, 0xC7, 0xE1, 0x54, 0x03, 0xE7, 0xCC, 0xC1, 0x85, 0x4F,
		0x0C, 0xE8, 0x62, 0xE6, 0x11, 0x7F, 0xC0, 0xD0, 0xDC, 0x51, 0x91, 0xCE, 0x43, 0xA3, 0x40,
		0xBC, 0xE9, 0x8B, 0x96, 0x23, 0x42, 0xF7, 0xB6, 0xD8, 0x65, 0x7A, 0x8D, 0x38, 0x49, 0x6D,
		0x4C, 0x5C, 0x2A, 0x8A, 0x6F, 0x1E, 0xF1, 0x09, 0xAA, 0x39, 0x2B, 0xA0, 0x01, 0xA9, 0xC8,
		0x83, 0x05, 0xD6, 0x02, 0x27, 0x45, 0x35, 0x13, 0xB8, 0x1A, 0x37, 0xBD, 0x41, 0xCB, 0xF0,
		0x55, 0x47, 0x56, 0x9B, 0xF4, 0x44, 0xF5, 0x16, 0x9E, 0xCF, 0xFB, 0x0F, 0xC3, 0x6E, 0xB7,
		0x67, 0x0B, 0xFA, 0x52, 0x94, 0x3E, 0x63, 0x5A, 0x8F, 0x22, 0x98, 0xA8, 0x59, 0x2E, 0x31,
		0x58, 0xD9, 0x17, 0xD5, 0x66, 0x6A, 0xB3, 0x07, 0xDB, 0xA2, 0xE2, 0xEE, 0x84, 0x18, 0x53,
		0xEB, 0xEC, 0x0A, 0x8E, 0xFD, 0x64, 0x1D, 0x5D, 0xAC, 0xA6, 0x19, 0xAD, 0x04, 0x24, 0xB4,
		0xB5, 0xE0, 0x06, 0xA7, 0x3D, 0x4B, 0x29, 0xA4, 0x7E, 0xED, 0x77, 0x79, 0x72, 0x69, 0x3A,
		0x99, 0x4A, 0xCA, 0xE3, 0x97, 0x0D, 0x30, 0xDE, 0x75, 0x2F, 0xA1, 0x7B, 0xAF, 0x7C, 0x48,
		0xAB, 0x8C, 0x74, 0xD1, 0x3F, 0x95, 0x3C, 0xD3, 0xE4, 0xD7, 0x78, 0x32, 0xA5, 0x89, 0xEA,
		0x92, 0xF8, 0xF2, 0x76, 0x26, 0x21, 0x9C, 0x15, 0xB9, 0xBB, 0x82, 0xD2, 0x6B, 0x81, 0x20,
		0x93, 0xC4, 0x46, 0x2C, 0x86, 0x36, 0x12, 0x80, 0x08, 0x57, 0x4E, 0x1F, 0xFC, 0xFE, 0xB0,
		0x5E, 0xC9, 0x6C, 0x2D, 0xCD, 0x1C, 0x28, 0x88, 0xDD, 0xEF, 0xDF, 0x00, 0x87, 0xBE, 0xBA,
		0xBF, 0xF9, 0x90, 0x61, 0xD4, 0xC2, 0xF6, 0x5B, 0x70, 0x0E, 0x71, 0x25, 0x50, 0x9F, 0x3B,
		0xFF
	},
	{
		0x2D, 0x97, 0x8F, 0xE8, 0x88, 0x1B, 0x6F, 0xF6, 0xC2, 0xD9, 0xBB, 0x51, 0xF4, 0x4B, 0x0C,
		0xDC, 0x0B, 0x36, 0xB2, 0xAA, 0xFA, 0x35, 0x5F, 0x8C, 0x85, 0x12, 0xCF, 0x31, 0x41, 0x84,
		0xC6, 0x04, 0x07, 0xF3, 0xA6, 0xCE, 0x43, 0x8E, 0x3E, 0x45, 0xB1, 0xB6, 0xAD, 0x2B, 0x7F,
		0x92, 0x9A, 0x89, 0x05, 0x9C, 0x0D, 0x73, 0x61, 0x30, 0x10, 0x9D, 0xAB, 0xEA, 0x86, 0x6A,
		0xC9, 0x1E, 0xE7, 0x5A, 0x9E, 0xBF, 0xCA, 0xC4, 0xB9, 0xA3, 0x96, 0xA5, 0x5E, 0xE4, 0x09,
		0x1F, 0xFD, 0xFB, 0xEE, 0x77, 0xD4, 0x06, 0xC8, 0xDE, 0x56, 0x57, 0xF9, 0xE5, 0x0E, 0xBC,
		0x60, 0x39, 0x53, 0x48, 0xD3, 0xCD, 0xDB, 0x14, 0x4F, 0xA8, 0x0F, 0xD8, 0x42, 0xC1, 0x80,
		0x7B, 0x46, 0x50, 0x54, 0x93, 0x58, 0xB3, 0x26, 0xF5, 0x22, 0x23, 0xF2, 0xB4, 0xBD, 0x01,
		0xAC, 0x74, 0xD7, 0x33, 0xA2, 0x4A, 0xE6, 0xD1, 0xDF, 0xD5, 0x67, 0x76, 0xB7, 0x03, 0x3B,
		0x3A, 0x5B, 0x8D, 0x69, 0x4D, 0x11, 0x49, 0x2E, 0xEC, 0x19, 0x7C, 0xBE, 0x08, 0x6D, 0x2A,
		0xBA, 0x70, 0xE1, 0x5C, 0x29, 0x3D, 0xB8, 0xDD, 0x17, 0x18, 0xE0, 0x02, 0x7A, 0x8A, 0x6C,
		0x20, 0x62, 0xE3, 0xCC, 0x4E, 0x82, 0x79, 0x2F, 0x38, 0x4C, 0xF8, 0x5D, 0x78, 0xF1, 0xE2,
		0x3C, 0x25, 0xA0, 0xF7, 0xC3, 0xA9, 0xFF, 0xEB, 0x87, 0x47, 0x55, 0x59, 0xAE, 0x81, 0x95,
		0x34, 0x83, 0x94, 0x7E, 0xD2, 0x9F, 0x2C, 0xC5, 0x71, 0xDA, 0x28, 0xED, 0x90, 0x1A, 0xFE,
		0xFC, 0x65, 0x24, 0xD0, 0x68, 0x27, 0x44, 0x75, 0x9B, 0x3F, 0xE9, 0x91, 0x40, 0x16, 0x15,
		0xC7, 0x52, 0x0A, 0x66, 0x98, 0xF0, 0x32, 0x63, 0xA1, 0xB5, 0x1D, 0xAF, 0x99, 0xCB, 0xB0,
		0x13, 0x21, 0xC0, 0xA4, 0xEF, 0x72, 0x37, 0xD6, 0x6E, 0xA7, 0x1C, 0x8B, 0x00, 0x64, 0x6B,
		0x7D
	}
};


typedef enum PROCESS_TYPE
{
	ENCRYPT = 0,
	DECRYPT = 1
};

const int KEYS_NUMBER = 256;

inline void process_data(const PROCESS_TYPE type, const BYTE(*keys)[KEYS_NUMBER], BYTE *pInData, BYTE *pOutData, const unsigned int uLen)
{
	for (unsigned int i = 0; i < uLen; ++i)
	{
		pOutData[i] = keys[type][ pInData[i] ];
	}
}

void printData(BYTE *data, int len)
{
    for (int i=0; i<len; i++)
        printf("0x%02X ", data[i]);

    printf("\n");
}


int main(int argc, char **argv)
{
    const int dataLen = 6;
    BYTE inputData[dataLen] = {0xC1, 0x06, 0xA9, 0x20, 0x9C, 0x2F};
    BYTE outputData[dataLen] = {};


    printf("Orig input data:\n");
    printData(inputData, dataLen);
    printf("\n");

    process_data(DECRYPT, client_keys, inputData, outputData, dataLen);

    printf("Data after DECRYPTING using client_keys:\n");
    printData(outputData, dataLen);
    printf("\n");

    printf("----------------------------------------\n");

    process_data(ENCRYPT, server_keys, outputData,outputData, dataLen);
    printf("Data after ENCRYPTING using server_keys:\n");
    printData(outputData, dataLen);
    printf("\n");
}

Output

Orig input data:
0xC1 0x06 0xA9 0x20 0x9C 0x2F

Data after DECRYPTING using client_keys:
0x81 0x6F 0x4E 0x07 0xB8 0x89

----------------------------------------
Data after ENCRYPTING using server_keys:
0xC1 0x06 0xA9 0x20 0x9C 0x2F