MechaCon

MechaCon is short for Mechanics Controller. This chip is the security ic of the PlayStation 2 that implements game disk security, Magic Gate and KELF file decryption.

There are two known main variants of it.

The earlier one is based on SPC 9700 and used till GH-016.

The newer one is ARM based, codenamed "Dragon".

The chip includes an 512 word eeprom. The content is different between the two main reversions.

SCP

TODO

Dragon

EEPROM layout

Start (word)	End (word)	Size (byte)	Description
0	48	96
48	90	84
96	128	64
128	150	44
160	190	60
192	198	12	Region params
204	208	8	MAC address
211	216	10	wake up time
216	225	18	model number
227	232	10	Region code key seed
232	237	10	Region code ciphertext
240	245	10	iLink id
245	248	6	(used by scmd 3, subcmd 48 and 49)
248	253	10	Console id
253	256	6	(used by scmd 3, subcmd 48 and 49)
256	312	112	config 2
312	344	64	config 0
344	400	112	config 1
400	512	224	Rom patches ciphertext

Region code decrypton

int getRegionFlags()
{
	// read kek
	uint8_t key508[8];
	ksGetKey(key508, 508);
	
	// read saved seed from eeprom
	uint8_t keyseed[10];
	eepromRead(227, sizeof(keyseed), keyseed);
	
	// read encrypted region from eeprom
	uint8_t ciphertext[10];
	eepromRead(232, sizeof(ciphertext), ciphertext);
	
	// generate key
	uint8_t key[8];
	desEncrypt(key508, keyseed, key);
	
	// decrypt ciphertext
	uint8_t plaintext[8];
	desDecrypt(key, ciphertext, plaintext);
	
	uint16_t crc = *(uint16_t *) plaintext;
	crc += *(uint16_t *) &plaintext[2];
	crc += *(uint16_t *) &plaintext[4];
	
	// check checksum
	if (crc  == *(uint16_t *) &plaintext[6])
		return *(uint32_t *) plaintext;
	
	retrun 0;
}

Rom patch

Decryption

bool readAndDecryptRomPatch()
{
	// read the patch's first half
	uint8_t patches[0xDE];
	eepromRead(400, 0x70, patches);
	
	// check if the -1th byte is 0 (sum is not checked)
	if (patches[0x6E])
		return false;

	// read the patch's second half
	eepromRead(456, 0x70, &patches[0x6E]);
	
	// check if the -1th byte is 0 (sum is not checked)
	if (patches[0x6E])
		return false;

	// read encryption key
	ksGetKey(key504, 504);
	
	// decrypt the patch using DES-ECB
	for (int i = 0; i < 0xD8; i += 8)
		desDecrypt(key504, &patches[i], &patches[i]);

	// check sum
	uint32_t sum = *(uint32_t *)patches;
	sum += *(uint32_t *)&patches[4];
	sum += *(uint32_t *)&patches[8];
	sum += *(uint32_t *)&patches[12];

	if (*(uint32_t *) &patches[0xD8] == ~sum)
		return false;
		
	return true;
}

Content

The patch can contain up to 4 patches.

addressX = The address where to apply the patch

valueX = The data that's written there

svc_addressX = The address where SVC X instruction jumps to.

payload = Arbitrary, could be code or data as well.

Offset	Size	Name
0x00	0x04	address0
0x04	0x04	address1
0x08	0x04	address2
0x0C	0x04	address3
0x10	0x04	value0
0x14	0x04	value1
0x18	0x04	value2
0x1C	0x04	value3
0x20	0x04	svc_address0
0x24	0x04	svc_address1
0x28	0x04	svc_address2
0x2C	0x04	svc_address3
0x30	0xA8	payload
0xD8	0x04	crc