Document digester

A cryptographic hash:The application calculates a 'cyptogragraphic hash value' of the uploaded data with the SHA-1 algorithm. Two files should have different cyptogragraphic hash functions if their content differ in any way (from just one changed bit to completely different documents). As the hash value is much smaller than the file itself there are, of course, files with different content but the same hash value. However, the cryptographic hash function is designed in a way that it is very hard ('impossible') to find two different files with identical hash values.
Therefore the hash-value can be used to identify a document.

Example:For the FACETS-ITN application we use this to get a written signature for an entire document: We ask applicants to send us a signed piece of paper with the SHA-1 digest value of the application .pdf file.