I'm not a crypto guru, but it seems to me that this issue can be crypto-anlayses somewhat like the speedups used to find hash collisions (if I understand them at all).
The goal in both cases is to find a hash that 'collides' with a known hash (password hash, or CC number of 6 BIN digits, 9,999,999,999 values and 1 checkdigit) from a known format. i.e pre-compute some portion of the salt+_static_string_portion, then brute-force the remainder of the string. As long as the salt is private or long enough, then does it matter? lyalc -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of T Biehn Sent: Tuesday, 11 August 2009 6:51 AM To: [email protected] Cc: full-disclosure Subject: Re: [Full-disclosure] Salted passwords Valdis, I don't have control over the set. Sorry I wasn't more explicit about this. Although, it should have been obvious that the solution needed to satisfy the conditions: Data to one way hash. The set has 9,999,999,999 members. Thanks for your input sweetie! -Travis On Mon, Aug 10, 2009 at 4:26 PM, <[email protected]> wrote: > On Sun, 09 Aug 2009 20:14:57 EDT, T Biehn said: >> Soliciting random suggestions. >> Lets say I have data to one-way-hash. >> The set has 9,999,999,999 members. > > Actually, if you're using a 10-digit decimal field, you probably have > 10**10 possible members - all-zeros counts too (unless there's *other* > reasons zero isn't a legal ID). It's those little off-by-one errors that tend to get you. > ;) > >> It's relatively easy to brute force this, or create precomp tables. > > That's because you only have 10M billion members to brute force against. > >> So you add a salt to each. > > A better idea cryptographically would be to fix the 10**10 member > limit, so that the set *could* have a much higher possible number of > members. Even staying at 10 characters, but allowing [A-Za-z0-9] (62 > possible chars) raises your space to 62**10 or about 8.3*10**17 (or almost 10M times the difficuly). > That's why most symmetric crypto algorithms use at least 64-bit or > even larger keys, and even larger for RSA and similar public-key systems. > > -- pgp http://pastebin.com/f6fd606da pgp _______________________________________________ Full-Disclosure - We believe in it. Charter: http://lists.grok.org.uk/full-disclosure-charter.html Hosted and sponsored by Secunia - http://secunia.com/ _______________________________________________ Full-Disclosure - We believe in it. Charter: http://lists.grok.org.uk/full-disclosure-charter.html Hosted and sponsored by Secunia - http://secunia.com/
