Hacking Genesis - Revision history

Rimsky82: /* Decryption */

2012-01-20T22:49:38Z

Decryption

← Older revision		Revision as of 22:49, 20 January 2012
Line 162:		Line 162:
	What we have left is a 40-bit string.		What we have left is a 40-bit string.

	The address is 24-bit and comprises of the following bytes, counted from high to low. 17-18-19-20-21-22-23-24~~-15-16~~-9-10-11-12-13-14-33-34-35-36-37-38-39-40		The address is 24-bit and comprises of the following bytes, counted from high to low. 17-18-19-20-21-22-23-24-9-10-11-12-13-14-15-16-33-34-35-36-37-38-39-40
	Which gives us -		Which gives us -
	<pre>		<pre>
	a = (s & 0xFF0000) \| ((s >> 10) & ~~0xC000) \| ((s >> 18) & 0x3F00~~) \| (s & 0xFF)		a = (s & 0xFF0000) \| ((s >> 16) & 0xFF00) \| (s & 0xFF)

	address = binary 000000001001110001110110, or 0x009C76		address = binary 000000001001110001110110, or 0x009C76

Rimsky82: /* Decryption */

2012-01-20T07:49:01Z

Decryption

← Older revision		Revision as of 07:49, 20 January 2012
Line 162:		Line 162:
	What we have left is a 40-bit string.		What we have left is a 40-bit string.

	The address is 24-bit and comprises of the following bytes, counted from high to low. 17-18-19-20-21-22-23-24-9-10-11-12-13-14-33-34-35-36-37-38-39-40		The address is 24-bit and comprises of the following bytes, counted from high to low. 17-18-19-20-21-22-23-24-15-16-9-10-11-12-13-14-33-34-35-36-37-38-39-40
	Which gives us -		Which gives us -
	<pre>		<pre>
	a = (((s >> 16) & ~~255) << 16~~) \| (((s >> 24) & ~~255) << 8~~) \| (s & ~~255~~)		a = (s & 0xFF0000) \| ((s >> 10) & 0xC000) \| ((s >> 18) & 0x3F00) \| (s & 0xFF)

	address = binary 000000001001110001110110, or 0x009C76		address = binary 000000001001110001110110, or 0x009C76
Line 173:		Line 173:
	Which gives us -		Which gives us -
	<pre>		<pre>
	v = (((s ~~>> 8)~~ & 7) << 13) \| (((s >> 11) & ~~31) << 8~~) \| (s >> 32)		v = ((s & 0x700) << 5) \| ((s >> 3) & 0x1F00) \| (s >> 32)

	value = binary 0101000001111000, or 0x5078		value = binary 0101000001111000, or 0x5078

Rimsky82 at 04:57, 24 November 2011

2011-11-24T04:57:03Z

← Older revision		Revision as of 04:57, 24 November 2011
Line 2:		Line 2:

	==Game Genie==		==Game Genie==

	[[Image:Genesisgenie.jpg\|Game Genie device for Sega Genesis]]		[[Image:Genesisgenie.jpg\|Game Genie device for Sega Genesis]]

	The Genesis game genie was different from all of the other genies in a couple ways. It was similar in that it intercepted ROM from the cartridge and overwrote certain bytes to achieve the desired effects. But besides obvious differences, like the shape and look of the device, the encryption scheme was also different. Genies on other systems used letters or hex digits to mask other hex digits, and swapped them around for good measure. The genesis genie actually used many different letters and numbers to mask 5-bit sequences, which were jumbled around. This was because the codes were 8 digits long, but needed to hold information for 5 bytes instead of 4.		The Genesis game genie was different from all of the other genies in a couple ways. It was similar in that it intercepted ROM from the cartridge and overwrote certain bytes to achieve the desired effects. But besides obvious differences, like the shape and look of the device, the encryption scheme was also different. Genies on other systems used letters or hex digits to mask other hex digits, and swapped them around for good measure. The genesis genie actually used many different letters and numbers to mask 5-bit sequences, which were jumbled around. This was because the codes were 8 digits long, but needed to hold information for 5 bytes instead of 4.

Rimsky82 at 04:56, 24 November 2011

2011-11-24T04:56:35Z

← Older revision		Revision as of 04:56, 24 November 2011
Line 2:		Line 2:

	==Game Genie==		==Game Genie==
			[[Image:Genesisgenie.jpg\|Game Genie device for Sega Genesis]]
	The Genesis game genie was different from all of the other genies in a couple ways. It was similar in that it intercepted ROM from the cartridge and overwrote certain bytes to achieve the desired effects. But besides obvious differences, like the shape and look of the device, the encryption scheme was also different. Genies on other systems used letters or hex digits to mask other hex digits, and swapped them around for good measure. The genesis genie actually used many different letters and numbers to mask 5-bit sequences, which were jumbled around. This was because the codes were 8 digits long, but needed to hold information for 5 bytes instead of 4.		The Genesis game genie was different from all of the other genies in a couple ways. It was similar in that it intercepted ROM from the cartridge and overwrote certain bytes to achieve the desired effects. But besides obvious differences, like the shape and look of the device, the encryption scheme was also different. Genies on other systems used letters or hex digits to mask other hex digits, and swapped them around for good measure. The genesis genie actually used many different letters and numbers to mask 5-bit sequences, which were jumbled around. This was because the codes were 8 digits long, but needed to hold information for 5 bytes instead of 4.

Rimsky82: started genie section

2011-11-24T04:49:38Z

started genie section

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Rimsky82: starting out with just headers and footers

2011-11-24T03:19:31Z

starting out with just headers and footers

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