An Identicon is a visual representation of a hash value, usually of an IP address, that serves to identify a user of a computer system as a form of avatar while protecting the user's privacy. The original Identicon was a 9-block graphic, and the representation has been extended to other graphic forms by third parties.

You can find the app here.

Don Park came up with the Identicon idea on January 18, 2007. In his words:

I originally came up with this idea to be used as an easy means of visually distinguishing multiple units of information, anything that can be reduced to bits. It's not just IPs but also people, places, and things. IMHO, too much of the web what we read are textual or numeric information which are not easy to distinguish at a glance when they are jumbled up together. So I think adding visual identifiers will make the user experience much more enjoyable.

A similar method had previously been described by Adrian Perrig and Dawn Song in their 1999 publication on hash visualization, which had already seen wide use such as in the random art of SSH keys.

ISC