Time to stop trusting paper

Add in World War 2, though, and you have the potential for a best seller. A recent book proposed a theory that Heinrich Himmler, head of the notorious SS in Nazi Germany, did not commit suicide, but was assassinated by British intelligence.

Martin Allen's Himmler's Secret War was the result of ten years' research in historical archives in the U.K. and abroad. But like all good conspiracy theories, there was a smoking gun. Buried in the U.K.'s National Archives, Allen found letters that cryptically refer to the treatment of "Little H", implying he had been "eliminated" by the British Political Warfare Executive, with a subsequent complete news blackout to cover it up.

So far, so good, but after the book was published cracks started to appear. Some of the language used in the letters didn't match the style of the time. Forensic analysis of the documents found pencil lines under the handwritten greetings and signatures. It soon became clear that the letters were contemporary forgeries.

But the story doesn't end there. There is no evidence that Allen had any suspicion the letters were fakes. The documents have only been viewed by a handful of people. So how did they get into the archive? Ironically, that question will probably generate more conspiracy theories than the original documents.

Well, like most repositories of historical material, the National Archives are very good at keeping things in, but not so good at keeping things out. We are all familiar with consultants droning on about confidentiality, integrity and availability, but tend to associate these issues with computing rather than physical things.

While there are a number of clever cryptological tricks we can use to authenticate electronic documents, it's much harder to do so with printed ones. This does not just apply to historians either. We are all well trained about "phishing" emails, but how good are you at detecting a forged document or security pass?

The intuitive trust that we put in physical objects such as documents, when compared to the suspicion with which we treat their electronic counterparts, is a potential weakness in many security systems.