Digital timestamping is the process of securely keeping track of the creation and modification time of a document. Security here means that no one–not even the owner of the document–should be able to change it once it has been recorded.

The mathematical basis for digital timestamping is provided by cryptographic hash functions which enable one to create a digest of a document or message; the digest reveals nothing about the message and it is impossible to find another message with the same digest. The administrative aspect involves setting up a publicly available, trusted timestamp management infrastructure to collect, process and renew timestamps.

History

The idea of timestamping information is actually centuries old. For example, when Robert Hooke discovered Hooke's law in 1660, he did not want to publish it yet, but wanted to be able to claim priority. So he published the anagram ceiiinosssttuv and later published the translation ut tensio sic vis. Similarly, Galileo first published one of his discoveries in the anagram form. A modern example is the case of an industrial research organization that may later need to prove, for patent purposes, that they made a particular discovery on a particular date; since magnetic media can be altered easily, this may be a nontrivial issue. One possible solution is for a researcher to compute and record in a hardcopy laboratory notebook a cryptographic hash of the relevant data file. In the future, should there be a need to prove the version of this file retrieved from a backup tape has not been altered, the hash function could be recomputed and compared with the hash value recorded in that paper notebook.

See also

• Cryptography
• Computer security
• Public key infrastructure

External links

• RSA Laboratories - What is digital timestamping? (http://www.rsasecurity.com/rsalabs/node.asp?id=2347)