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c330156259
Finding even semi-official test vectors for this CRC implementation was hard, because it turns out not to _quite_ match any of the well known ones catalogued on the web. Its _polynomial_ is well known, but the combination of details that go alongside it (starting state, post-hashing transformation) are not quite the same as any other hash I know of. After trawling catalogue websites for a while I finally worked out that SSH-1's CRC and RFC 1662's CRC are basically the same except for different choices of starting value and final adjustment. And RFC 1662's CRC is common enough that there _are_ test vectors. So I've renamed the previous crc32_compute function to crc32_ssh1, reflecting that it seems to be its own thing unlike any other CRC; implemented the RFC 1662 CRC as well, as an alternative tiny wrapper on the inner crc32_update function; and exposed all three functions to testcrypt. That lets me run standard test vectors _and_ directed tests of the internal update routine, plus one check that crc32_ssh1 itself does what I expect. While I'm here, I've also modernised the code to use uint32_t in place of unsigned long, and ptrlen instead of separate pointer,length arguments. And I've removed the general primer on CRC theory from the header comment, in favour of the more specifically useful information about _which_ CRC this is and how it matches up to anything else out there. (I've bowed to inevitability and put the directed CRC tests in the 'crypt' class in cryptsuite.py. Of course this is a misnomer, since CRC isn't cryptography, but it falls into the same category in terms of the role it plays in SSH-1, and I didn't feel like making a new pointedly-named 'notreallycrypt' container class just for this :-) |
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| .. | ||
| colours.txt | ||
| cryptsuite.py | ||
| display.txt | ||
| eccref.py | ||
| lattrs.txt | ||
| scocols.txt | ||
| testcrypt.py | ||
| utf8.txt | ||
| vt100.txt | ||