The salt is similar to an identifier.

kinda. The salt is more like a pointer into a set of "hashed" values (not hash as in perl hash but hash as in hash function). The whole purpose of salt is to prevent dictionary attacks by creating a much larger pool of hashed passwords from the same plaintext.

I've heard specific algorithms use specfic salts

Somewhat true. For some versions of the crypt function, the format of the hashed value is different based on the algorithm (YMMV): 

Standard DES-based encryption has a two character salt
Extended DES-based encryption has a nine character salt
MD5 encryption has a twelve character salt starting with $1$
Blowfish encryption has a sixteen character salt starting with $2$

I believe perl uses either 3DES or DES.

Possibly. It may be DES, Extended DES, MD5, Blowfish or whatever else your c library crypt provides.

For great reading about the crypt function and salt, check out Robert Morris and Ken Thompson's seminal work - Password Security: A Case History ( Communications of the ACM, 22(11):594-597, November 1979). Here's a google cache link

-derby

In reply to Re: Re: Tales from the crypt() by derby
in thread Tales from the crypt() by Cody Pendant

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.