Thanks Simon. And now that I can read it... ;-)
* need more detail on salt and format and allowed characters. For some reason the man page on crypt-256/512 is very specific on the allowed salt alphabet, etc. * need reference to base64, most likely http://tools.ietf.org/html/rfc3548 As I learned the hard way there several, and crypt-256/512 uses a very custom one. * looking at the name/value pairs, if a single variable, in one order, case sensitive isn't so bad. However, I'll re-read Solr's other ideas * "where N, r and p are unsigned decimal numbers" this probably needs more details on allowable ranges and types, e.g. "positive integers" Copying the spec isn't bad here, but I need to think how this can be simplified. N CPU/Memory cost parameter, must be larger than 1, a power of 2 and less than 2^(128 * r / 8). r Block size parameter. p Parallelization parameter, a positive integer less than or equal to ((2^32-1) * hLen) / MFLen where hLen is 32 and MFlen is 128 * r. * needs something on happens on error if parameters are misformed or incorrect or out of range. * I'd add a references section Just made a gitorious account under 'ngalbreath' I'm happy to make these changes. thanks! nickg On Tue, Sep 18, 2012 at 11:05 AM, Simon Josefsson <[email protected]> wrote: > Sorry, the repository was renamed... see here instead: > > https://www.gitorious.org/scrypt/scrypt-unix-crypt/blobs/master/unix-scrypt.txt > > /Simon > > Nick Galbreath <[email protected]> writes: > >> https://www.gitorious.org/scrypt/scrypt/blobs/master/unix-scrypt.txt >> >> has vanished! (or I get a 404) >> >> >> >> On Tue, Sep 18, 2012 at 5:10 AM, Simon Josefsson <[email protected]> wrote: >>> Solar Designer <[email protected]> writes: >>> >>>> On Tue, Sep 18, 2012 at 08:51:06AM +0200, Simon Josefsson wrote: >>>>> We could start it as a parallel effort though. Would you like to help >>>>> work on this? I started a document here: >>>>> >>>>> https://www.gitorious.org/scrypt/scrypt/blobs/master/unix-scrypt.txt >>>> >>>> FWIW, I am planning to do some research/testing/benchmarking of scrypt >>>> for this kind of uses very soon. Chances are that I'll want to make >>>> modifications to scrypt proper as a result - probably at least have an >>>> optional time-memory tradeoff defeater (a fourth parameter) as briefly >>>> discussed with Colin on the crypt-dev list. Naturally, I expect some >>>> healthy resistance to any proposed modifications to scrypt, now that >>>> it's been around for 3 years and is about to get standardized. Yet I >>>> think this is something to discuss and consider. >>>> >>>> There are also some difficulties with using scrypt as a crypt(3) >>>> password hash type. As discussed on crypt-dev, scrypt at <= 1 MB (yes, >>>> misuse of it) is not a good replacement for bcrypt, whereas scrypt at >>>> much larger memory settings (proper use) should better be used with >>>> concurrency limits (not currently found inside crypt(3) implementations, >>>> nor in many crypt(3)-using daemons). So the issue is a bit non-trivial. >>> >>> Yes selecting parameters is difficult. I'm also concerned that too >>> small parameters end up being weaker than PBKDF2/bcrypt. Generally, I'm >>> not entirely sure how one would use scrypt for authentication services >>> -- probably the best is to reserve a chunk of memory and setup a scrypt >>> computation service. You would then have no issues up until some >>> pre-determined number of authentications/second, that you could >>> rate-limit per-user on. >>> >>>> Speaking of the encoding syntax, I think the key=value,... style of >>>> syntax is probably a bad idea. It complicates parsing and brings up >>>> unnecessary questions such as whether a parser is supposed to handle >>>> keys in the one standard order only or in any order, etc. IIRC, the >>>> "rounds=..." thing first appeared in SunMD5, then was reused for >>>> SHA-crypt, and well, there were some parsing ambiguities with them. It >>>> might be better to just allocate a fixed number of base-64 characters at >>>> the start of the string (right after the $7$ or whatever hash type >>>> prefix) to correspond to the parameters. And if we need to add an extra >>>> parameter later, we just pick a new prefix (call it e.g. $7a$). I used >>>> a similar approach in phpass "portable hashes", where the character >>>> right after the $P$ prefix holds base-2 logarithm of the iteration >>>> count. This is trivial to parse and encode, and there's just one valid >>>> encoding. So I suggest that we try not to make things more flexible >>>> than we actually need them to be. >>> >>> Excellent, this was the kind of feedback I was hoping for. I agree. If >>> you have a gitorious account and want to help with the document, I'll >>> add you. >>> >>> /Simon
