How are timestamps different from digital signatures?
Timestamps and digital signatures are related and complementary technologies. While digital signatures answer the question of who signed a particular document, timestamps answer the question of when the document was signed or created or last modified, as well as being able to tell whether a document has been modified since being timestamped. In this sense, timestamps can be used to prove historical integrity. Digitally signed transactions use timestamping to ensure that the signing key was valid at the time of signing. This protects against future claims by the signer that the document was not signed by him/her (non-repudiation). For applications where formal authentication is not required, timestamps by themselves can provide proof of data integrity.
