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Information about Time Stamp

For the ICMP message, see ICMP Timestamp.


Timestamp can refer to a time code or to a digitally signed timestamp whose signer vouches for the existence of the signed document or content at the time given as part of the digital signature.

Timestamps are very useful for logging events.

Examples 2005-10-30 10:45 Sat Jul 23 02:16:57 2005

Many sources also use the term timestamp to refer specifically to Unix time, the number of seconds since 00:00:00 UTC on January 1, 1970.

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 (Latin for "as is the extension, so is the force"). Similarly, Galileo first published his discovery of the phases of Venus 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.

Trusted (Digital) Timestamping

Enlarge picture
Getting a timestamp from a trusted third party.
Trusted 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 provided that the timestamper's integrity is never compromised. The administrative aspect involves setting up a publicly available, trusted timestamp management infrastructure to collect, process and renew timestamps.

A trusted timestamp is a timestamp issued by a trusted third party (TTP) acting as a timestamping authority (TSA). It is used to prove the existence of certain data before a certain point (e.g. contracts, research data, medical records,...) without the possibility that the owner can backdate the timestamps. Multiple TSAs can be used to increase reliability and reduce vulnerability.

Creating a timestamp

The technique is based on digital signatures and hash functions. First a hash is calculated from the data. A hash is a sort of digital fingerprint of the original data: a string of bits that is different for each set of data. If the original data is changed then this will result in a completely different hash. This hash is sent to the TSA. The TSA concatenates a timestamp to the hash and calculates the hash of this concatenation. This hash is in turn digitally signed with the private key of the TSA. This signed hash + the timestamp is sent back to the requester of the timestamp who stores these with the original data (see diagram).

Since the original data can not be calculated from the hash (because the hash function is a one way function), the TSA never gets to see the original data, which allows the use of this method for confidential data.

Simple solution used in previous times was to post sensitive data via official state post service to your own address, since post stamp is an official time-stamp recognized in court.

Checking the timestamp

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Checking correctness of a timestamp generated by a time stamping authority (TSA).
Anyone trusting the timestamper can then verify that the document was not created after the date that the timestamper vouches. It can also no longer be repudiated that the requester of the timestamp was in possession of the original data at the time given by the timestamp. To prove this (see diagram) the hash of the original data is calculated, the timestamp given by the TSA is appended to it and the hash of the result of this concatenation is calculated, call this hash A.

Then the digital signature of the TSA is to be checked by decrypting the signed hash given by the TSA with the public key of the TSA. This results in the decrypted hash, let us call this hash B. If hash A equals hash B then the timestamp is unaltered and was issued by the TSA. If not, then either the timestamp was altered or the timestamp was not issued by the TSA.

External links

Lecture Notes in Computer Science

See also

The Timestamp is an ICMP message which is used for time synchronization. It consists of the originating timestamp.

Message Format:

00 01 02 03
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time code is a sequence of numeric codes generated at regular intervals by a timing system. Time codes are used extensively for synchronization, and for logging material in recorded media.
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digital signature or digital signature scheme is a type of asymmetric cryptography used to simulate the security properties of a signature in digital, rather than written, form.
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Data logging is the practice of recording sequential data, often chronologically.

Etymology

To log is a verbed derivative of the noun logbook; the verb form means to record in a logbook, and may have been coined in the 1820s.
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Unix time, or POSIX time, is a system for describing points in time: it is the number of seconds elapsed since midnight UTC of January 1 1970, not counting leap seconds. It is widely used not only on Unix-like operating systems but also in many other computing systems.
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Robert Hooke, FRS (July 18, 1635 – March 3, 1703) was an English polymath who played an important role in the scientific revolution, through both experimental and theoretical work.
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Hooke's law of elasticity is an approximation that states that the amount by which a material body is deformed (the strain) is linearly related to the force causing the deformation (the stress).
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16th century - 17th century - 18th century
1630s  1640s  1650s  - 1660s -  1670s  1680s  1690s
1657 1658 1659 - 1660 - 1661 1662 1663

:
Subjects:     Archaeology - Architecture -
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anagram (Greek anagramma 'letters written anew', passive participle of ana- 'again' + gramma 'letter') is a type of word play, the result of rearranging the letters of a word or phrase to produce other words, using all the original letters exactly once; e.
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Galileo Galilei

Portrait of Galileo Galilei by Giusto Sustermans
Born January 15 1564(1564--)[1]
Pisa, Tuscany - Italy
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Computer security is a branch of information security applied to both theoretical and actual computer systems. Computer security is a branch of computer science that addresses enforcement of 'secure' behavior on the operation of computers.
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digital signature or digital signature scheme is a type of asymmetric cryptography used to simulate the security properties of a signature in digital, rather than written, form.
..... Click the link for more information.
A hash function [1] is a reproducible method of turning some kind of data into a (relatively) small number that may serve as a digital "fingerprint" of the data. The algorithm "chops and mixes" (i.e.
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digital signature or digital signature scheme is a type of asymmetric cryptography used to simulate the security properties of a signature in digital, rather than written, form.
..... Click the link for more information.
Public-key cryptography, also known as asymmetric cryptography, is a form of cryptography in which a user has a pair of cryptographic keys - a public key and a private key. The private key is kept secret, while the public key may be widely distributed.
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A hash function [1] is a reproducible method of turning some kind of data into a (relatively) small number that may serve as a digital "fingerprint" of the data. The algorithm "chops and mixes" (i.e.
..... Click the link for more information.
Do one-way functions exist?
A one-way function is a function that is easy to compute but "hard to invert" (in the sense defined below). "Easy to compute" means that some algorithm can compute the function in polynomial time (in the input size).
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Hash may refer to:
  • Number sign, #, also called "pound sign" in the USA
  • Hashish, a psychoactive drug derived from the Cannabis plant
  • Hash Bash, an annual event in Ann Arbor, Michigan

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digital signature or digital signature scheme is a type of asymmetric cryptography used to simulate the security properties of a signature in digital, rather than written, form.
..... Click the link for more information.
Public-key cryptography, also known as asymmetric cryptography, is a form of cryptography in which a user has a pair of cryptographic keys - a public key and a private key. The private key is kept secret, while the public key may be widely distributed.
..... Click the link for more information.
Cryptography (or cryptology; derived from Greek κρυπτός kryptós "hidden," and the verb γράφω gráfo "write" or λεγειν legein
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Computer security is a branch of information security applied to both theoretical and actual computer systems. Computer security is a branch of computer science that addresses enforcement of 'secure' behavior on the operation of computers.
..... Click the link for more information.
digital signature or digital signature scheme is a type of asymmetric cryptography used to simulate the security properties of a signature in digital, rather than written, form.
..... Click the link for more information.
A Digital Postmark (DPM) is a technology that applies a trusted time stamps issued by a Postal Authority to an electronic document, validates electronic signatures, and stores and archives all non-repudiation data needed to support a potential court challenge.
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A Digital Postmark (DPM) is a technology that applies a trusted time stamps issued by a Postal Authority to an electronic document, validates electronic signatures, and stores and archives all non-repudiation data needed to support a potential court challenge.
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Smart contracts are computer protocols that facilitate, verify, or enforce the negotiation or performance of a contract, or that obviate the need for a contractual clause. Smart contracts usually also have a user interface and often emulate the logic of contractual clauses.
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Unix time, or POSIX time, is a system for describing points in time: it is the number of seconds elapsed since midnight UTC of January 1 1970, not counting leap seconds. It is widely used not only on Unix-like operating systems but also in many other computing systems.
..... Click the link for more information.


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