if your challenge of the day is only changed once per day, once an attacker has sniffed the username and hash, those are all they need to get in for the rest of the day. you can improve it somewhat by including the client's IP address in the hash, but this will cause problems if they're behind a proxy, etc. and it still isn't 100% solid because IP addresses can be spoofed.

the only truly secure way to authenticate over an insecure channel without using encryption is with a zero knowledge proof, but implementing a ZKP is a complex undertaking since it is necessarily interactive and would require sophisticated client-side action. the chances of screwing something up in the implementation and wrecking the security are probably high enough that it's not worth even considering.

if i were you and i were really concerned about security, i would run everything over https and use basic HTTP authentication. it's simple and about as secure and reliable as you're going to get.

also, it sounds like you're storing passwords on the server in some unencrypted form. this is almost always a bad idea.

there's no such thing as perfect security. the best you can do is to make it hard enough to crack that the expense of cracking it would be more than any possible reward that the attacker would get.

anders pearson

In reply to Re: Re: Re: Securing Web Apps. by thraxil
in thread Securing Web Apps. by jdtoronto

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.