Programming Jabber

jabber:x:signed

The jabber:x:signed namespace is related to the jabber:x:encrypted namespace and is used to stamp <presence/> and <message/> elements with a PKI-based signature, thus providing reliable identification of the packet originator.

In generating the signature block, some relevant data must be used to pass into the signing algorithm so that an electronic signature is produced. In the case of <presence/> elements, the contents of the <status/> tag are used, and in the case of <message/> elements, the contents of the <body/> tag are used.

The presence of a jabber:x:signed signature in a <presence/> packet is intended to signify that the client sending the packet supports such PKI infrastucture and, for example, is able to decrypt messages encrypted in the jabber:x:encrypted namespace.

Here’s a <presence/> packet containing a signature; the data “All present and correct” is what is fed into the algorithm:

SEND: <presence from='[e-mail]' to='[e-mail]'>
  <status>All present and correct</status>
  <x xmlns='jabber:x:signed'>
    p/B8CuePDUvAAHPuacDb2OYjAHTGn4BbqChrhxwH8ZTKJxL
    9nUNH58OF=tl0VMDcSYizG5HFh
  </x>
</presence>