The library is a Common Lisp implementation of the two algoritms:
- The MD5 Message-Digest Algorithm, as defined in RFC 1321 by R. Rivest published in April 1992.
- The MD5 APR algorithm used for basic authorization by web servers Apache, Nginx, and others as well as by the htpasswd password encryption utility.
Ystok-MD5 is based on Pierre R. Mai's MD5.
On LispWorks, the library switches to a specialized code that uses a fast raw 32bit arithmetic introduced in LW 4.4. This version demonstrates speed increase of about two hundred times compared to a naive port.