e-TimeStamp: Overview

1. What is e-TimeStamp?

e-TimeStamp gives you unequivocal proof that the contents of your work existed at a point-in-time and that the contents have not changed since that time. Consider this a type of notary service - only updated to become a digital notary. Any file on your computer can be TimeStamped, regardless of its content.

• Inexpensive to operate
• Confidential and reliable to use
• Quick and easy to get started (see installation)

2. What is a digital time-stamping service?

A digital time-stamping service (DTS) issues time-stamps which associate a date and time with a digital document in a cryptographically strong way. The digital time-stamp can be used at a later date to prove that an electronic document existed at the time stated on its time-stamp. For example, a physicist who has a brilliant idea can write about it with a word processor and have the document time-stamped. The time-stamp and document together can later prove that the scientist deserves the Nobel Prize, even though an arch rival may have been the first to publish.

Here's one way such a system could work. Suppose Alice signs a document and wants it time-stamped. She computes a message digest of the document using a secure hash function and then sends the message digest (but not the document itself) to the DTS, which sends her in return a digital time-stamp consisting of the message digest, the date and time it was received at the DTS, and the signature of the DTS. Since the message digest does not reveal any information about the content of the document, the DTS cannot eavesdrop on the documents it time-stamps. Later, Alice can present the document and time-stamp together to prove when the document was written. A verifier computes the message digest of the document, makes sure it matches the digest in the time-stamp, and then verifies the signature of the DTS on the time-stamp.

To be reliable, the time-stamps must not be forgeable. Consider the requirements for a DTS of the type just described:

1. The DTS itself must have a long key if we want the time-stamps to be reliable for, say, several decades.
2. The private key of the DTS must be stored with utmost security, as in a tamperproof box.
3. The date and time must come from a clock, also inside the tamperproof box, which cannot be reset and which will keep accurate time for years or perhaps for decades.
4. It must be infeasible to create time-stamps without using the apparatus in the tamperproof box.

3. Why digital certificates alone are not enough?

A digital certificate only provides the identity of a person or a company in any electronic transaction or action, but not the time of performing the action. If a secure, reliable third-party time source is a key element in the business transaction or the situation, timestamping service is needed.

4. Why should I use timestamping in e-commerce?

Using timestamping in e-commerce can prove that transactions occur at particular time and the contents have not been altered since then. The contents of transactions are kept confidential. Using timestamping service can prevent fraud and repudiation on time. Customers and suppliers will have confidence in buying and selling on the Internet.


5. Who can make use of timestamping service?

Timestamping can be applied to many areas. The following is some examples of making use of timestamping:

• Anyone with intellectual property, such as ideas, designs, images and books, can make use of timestamping service to witness their copyrights online and protect their intellectual properties.
• Corporations can use timestamping service in e-commerce, especially those time-sensitive ones, to prevent fraud and repudiation.
• Accountants can close the financial books electronically and timestamp them to prove that they have not been altered since then.