Validity of Digital Signatures

How long a digital signature remains valid depends on who has issued it. Usually the validity ranges from 1-2 years. Every issuing company has its own product specification that varies according to its target market. The good news though is that digitally signed documents can be time-stamped digitally, so that even after the key expires, the signature can be validated.

 This comes in handy when you have digitally signed a contract or agreement that will stay in force beyond the validity period of the signature, e.g. long-term leases. All parties to the contract must retain the time-stamp copy.  If the document is time-stamped, then even if the signer’s key is compromised later on, the contract’s validity can be proved by this time-stamp.