How are Intervals chained in the ProofMark System?

The ProofMark Server creates Intervals contiguously in a chain that continues to lengthen with the passage of time (rather like a stream of ticker tape issued by stock ticker machines invented in the late 1800's).

The start time of the very first Interval in the chain is known as the chain start time, and is stored in each Interval. While theoretically possible, it is unlikely that two different servers would be configured with the same server-id (the hostname[:port] of the server). It is highly improbable that these servers could also be started at exactly the same time, resulting in identical chain start-times. Therefore, adding the chain start time to the server-id uniquely identifies an Interval chain. Once the chain is identified, an Interval within the chain is uniquely identified by the Interval's start time. The chain's Intervals are stored persistently in an archive.

During each Interval, the private key is used in the creation of ProofMarks, which are the timestamping and authenticity certificates. Many ProofMarks can be issued during an Interval, each signed by the Interval's private key.

Certifying data using a ProofMark is very straightforward: the submitted data is simply signed by the Interval private key. The original data, the signature, and the Interval public key are all included in the ProofMark. One can now simply use published cryptographic routines to verify that public key applied to the signature resolves to the original data, illustrating the self-contained integrity "seal" provided by a ProofMark.

The start time within each Interval coupled with the chain start time form an unbroken sequence of public keys that can be used to fix a ProofMarks position in time, which also fixes the exact state of a set of data at that point in time. To prove this state at some future point, the chain of public keys is posted to an easily accessible place (i.e. several web servers) from where they can be used to verify a ProofMark (see Verification below).