Not plain timestamps, but there is such as thing as a trusted Time Stamping Authority which will sign a document hash + timestamp to prove that information exis

Not plain timestamps, but there is such as thing as a trusted Time Stamping Authority which will sign a document hash + timestamp to prove that information existed before a certain date. http://en.wikipedia.org/wiki/Trusted_timestamping http://en.wikipedia.org/wiki/Trusted_timestamping