Scripsit Peter Samuelson <[EMAIL PROTECTED]> > For large files, getting a cryptographic checksum is more about reading > blocks off the disk than about CPU time. So it wouldn't be completely > ridiculous to allow sha-1 to remain ambiguous with competing 160-bit > hashes, and have --check check for all of them (reading the file only > once).
That sounds cryptographically unsafe. It would mean that a practical preimage attack against _any_ of the supported hashes would break the entire system. That's not the kind of algorithm agility we need. > I still think two-byte prefixes for non-md5-non-sha1 hashes makes some > sense, like s- for sha-256. That is much better. But let's use "s." as a prefix and do a [/+] -> [_-] substitution on the following base64 data. The dot in the prefix will prevent the prefix from being mistaken as part of a slightly larger non-tagged hash value. >> $ dsum -a sha1 foo; sha1sum foo >> f572d396fae9206628714fb2ce00f72e94f2258f foo >> f572d396fae9206628714fb2ce00f72e94f2258f foo There appears to be to few characters of hash there, at least unless it is a cosmically weird coincidence that it base64 encodes to all hex digits. :-) I would expect something like $ dsum -a sha1 COPYING; sha1sum COPYING s.w4runjyMTV1ZT_VIob4FRTAjAW1ihpMfZRLbIV7B_UI COPYING s.w4runjyMTV1ZT_VIob4FRTAjAW1ihpMfZRLbIV7B_UI COPYING $ dsum -a sha1 -a md5 COPYING s.w4runjyMTV1ZT_VIob4FRTAjAW1ihpMfZRLbIV7B_UI COPYING 4325afd396febcb659c36b49533135d4 COPYING $ echo moooooooo | sha1sum - s.-tUTs04N4IxBOtWpdoIXt1b0qgHIgNm9IC_OgYjm-mU - -- Henning Makholm "But I am a Sunni Muslim," the bemused Arab said. -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]