The long-term signature is an electronic signature endowed with validity over time. All certificates in the chain of trust and the result of the verification of their validity at the time the signature was made are included in the electronic signature. It also includes a time stamp to guarantee the exact moment in which the electronic signature was produced. 

The time stamp is periodically updated to ensure that the information that was signed with valid algorithms in its day does not lose its value since these may eventually be insecure due to technological evolution. Resealing the information with secure cryptographic algorithms at all times offers security guarantees of permanence of value over time.