A long established use of the hashing technique is straightforward content validation. As even the slightest conceivable change to a document will dramatically affect its hash value, the content of any document can be instantly validated by comparing its current hash value to the hash value its author claims it should have. What Codel adds to that simple procedure is the trusted storage of the author's original hash in such a way that even the author cannot cheat the system. Our mechanism for achieving that trust that is our own Audit Trail Protection protocol.
It is important to distinguish Content Protection from Uniqueness. It is all very well being able to prove that your airline ticket bears the right content and says what it is supposed to say. You are on the right flight, going to the right destination, returning on the correct date, etc. But its also rather useful to know that no one else can be sold your seat for that flight. Only monitoring of unique identifiers can provide that assurance.
Content protection can, of course, be used just as well to protect millions of identical documents as it can to protect one unique document.
