13.7. Document Signature

SavaPage generates a digital signature for every document printed-out or downloaded. Digital signatures are generated using a cryptographic technique called Hash-based Message Authentication Code (HMAC)[30]. The algorithm takes various output job attributes such as job time, user name, document name and UUID, and combines them with a secret key. The result is then passed through the MD5 digest algorithm. The resulting signature is unique to the document instance [31]. The applied secret key ensures the authenticity of the signature.

The algorithm used is:

where

Note

The signature is stored in the database for future use.



[31] The SHA1 digest algorithm is a stronger alternative, but MD5 is secure enough for our application and generates shorter signatures, which are easier to enter as argument to find the matching document.