Editing Digital Audio Access Protocol (section)

== DAAP authentication ==
Beginning with iTunes 4.2, Apple introduced authentication to DAAP sharing, meaning that the only clients that could connect to iTunes servers were other instances of iTunes. This was further modified in iTunes 4.5 to use a custom hashing algorithm, rather than the standard [[MD5]] function used previously. Both authentication methods were successfully reverse engineered within months of release.<ref name="slash 4.5 cracked">{{cite web|url=http://apple.slashdot.org/apple/04/04/29/1554231.shtml|title=iTunes 4.5 Authentication Cracked|date=April 29, 2004|accessdate=March 12, 2007}}</ref>

With iTunes 7.0, a new 'Client-DAAP-Validation' header hash is needed when connecting to an iTunes 7.0 server. This does not affect third-party DAAP servers, and all DAAP clients without support for this feature, including iTunes itself before version 7.0, will fail to connect to an iTunes 7.0 server, receiving a '403 Forbidden' HTTP error. The iTunes 7.0 authentication [[traffic analysis]] seem to indicate that a certificate exchange is performed to calculate the hash sent in the 'Client-DAAP-Validation' header.