Time Stamp Authority ( PKI )
Digital certification authority, similar to a CA . Its service is to certificate the binding between a document (or, more generally, a stream of bytes) and a date for that document.
The TSA releases a sort of digital certificate, called Time Stamp, that wrap the document certified and contains the date, expressed in a generalised time format; it contains informations about the digital certificate of the user that originated the request of Time Stamp for his document, too.