Gits2012teaser

#2 AL's Revenge

• file 49dd327824d5afe9cdf931ea4b13719f.bin says xz compressed file -> xzcat > f
• file f says LLVM bitcode -> llvm-dis > f.s (only works with LLVM 2.8, not with 3.0)
• analyze disassembly, extract C representation:

int
VerifySerial(uint64_t name, uint64_t serial)
{
	uint64_t a = 0x8000000000000000LL;
        uint64_t b = 0xa348fccd93aea5a7LL;
	uint64_t result = 0;

	/* high order bit set? */
	if (name & a)
		a ^= b;

	if (serial & a)
		serial ^= b;

	while (serial != 0) {
		if (serial & 1)
			result ^= name;

		serial >>= 1;
		name <<= 1;

		if (name & a)
			name ^= b;
	}

	return (result == 1);
}