Look into one-time password schemes using S/Key. (I think there are Perl modules the handle this, like Crypt::SKey.) It works the following way:

  1. You and the user have a share secret passphrase.
  2. When the user first logs in, she is asked to provide a challenge password based on N MD5-iterations of the passphrase (S/Key converts the MD5 hex digits into a small group of 3-5 letter words so it's easy for a user to type)
  3. Each time the user logs in, the password is based on N-1 iterations. So there's no way a hacker could determine this (well, a crypto guru with that knowledge probably won't care to hack your web site since some three letter agency is paying her big money to do more interesting things ;)
  4. When it nears zero, the user resets the passphrase to something different. (Usually initial N is something like 1000)

Information on S/Key can be found at http://lheawww.gsfc.nasa.gov/~srr/skey_info.html.

In reply to S/Key (was "Re: Web Security for CGI programs") by rrwo
in thread Web Security for CGI programs by Stamp_Guy

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.