As soon as all the signatories have electronically signed the document, Scrive creates a unique, digital fingerprint of the file containing: the document, the Evidence Package, and any attachments. To generate this fingerprint, we apply a mathematical function to produce a value known as a cryptographic hash.
It’s impossible to generate an identical hash value using any other file or method (theoretically it’s possible, but the time required is longer than the current age of the Universe). And the nature of a cryptographic hash is such that it can’t be used to re-create the document’s content.
Guardtime organises the hash values of multiple documents into a structure known as a Merkle tree. The combined hash values of all the documents in the Merkle tree are used to compute a single hash value which is assigned to the root of the tree, the top level hash.
Note that diagrams of Merkle trees may depict the root of the tree at the top or the bottom. The important concept is that the top level hash is the root of the tree. It is mathematically linked to all the other hashes in the tree in such a way that you can verify your document’s integrity as long as you have:
- the sealed document
- access to the top level hash AND trust in its validity.
Your access to the top level hash depends on whether or not you store your documents in the Scrive E-archive, as explained below.