Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > sci.crypt > #32839

Re: storing passwords

Show all headers | View raw

"David Eather" <eather@tpg.com.au> writes:
> I have a salt and a large secret password (hard-coded into the tamper
> proof design) such that the length of the salt and password makes
> inverting a hash function practically impossible. To that I append a
> short counter and the combined salt & long password & counter is
> hashed to give a user password.

The details are usually a bit different but the above is basically a
standard scheme.  You'd have a large key K in the device, and the user
password can be something like HMAC(K, userid) truncated to the amount
of bits you want to give to the user.  You'd typically generate K itself
from some other master secret in the device, for more flexibility; add
more indirection or another counter so the user can change passwords,
etc.  The verification would be done in the module so when you check a
password, you just get a yes or no, you never get to see the hash.

> Other than such tamper proof hardware not existing and not being able
> to choose your own passwords is there some other flaw I have missed?

The tamper proof (or at least resistant) device is also standard, and
called a host security module (HSM).  The ones actually sold as HSM's
are expensive because they're used in industries that are fairly
insensitive to cost, but they are basically microprocessor boards in
tamper resistant enclosures.  You can do similar things with smart
cards, whose tamper resistance these days is quite good, thpugh they are
much slower than HSM's.  Of course you will have to make security and
design decisions around the possibilities of the cards or HSMs being
stolen, breaking, etc.

Back to sci.crypt | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

storing passwords "David Eather" <eather@tpg.com.au> - 2015-10-14 06:28 +1000
  Re: storing passwords Jakob Bohm <jb-usenet@wisemo.com> - 2015-10-13 23:06 +0200
    Re: storing passwords "David Eather" <eather@tpg.com.au> - 2015-10-15 08:45 +1000
  Re: storing passwords Paul Rubin <no.email@nospam.invalid> - 2015-10-13 14:22 -0700
    Re: storing passwords Jakob Bohm <jb-usenet@wisemo.com> - 2015-10-13 23:42 +0200
      Re: storing passwords Paul Rubin <no.email@nospam.invalid> - 2015-10-13 14:48 -0700
        Re: storing passwords Jakob Bohm <jb-usenet@wisemo.com> - 2015-10-14 00:09 +0200
          Re: storing passwords <william@wilbur.25thandClement.com> - 2015-10-16 18:08 -0700
            Re: storing passwords Jakob Bohm <jb-usenet@wisemo.com> - 2015-10-19 15:51 +0200
  Re: storing passwords "David Eather" <eather@tpg.com.au> - 2015-10-15 08:45 +1000
  Re: storing passwords Jeffrey Goldberg <nobody@goldmark.org> - 2015-10-15 15:51 -0500

csiph-web