Timestamp format
Timestamp format and the rest of the theoretical part is created by
"Open PGP in Russia".
For cryptographical operations are used standards and formats of PGP.
Or, in other words, timestamps given by service can be checked by standard PGP programs.
Open PGP Message Format
Using "Open PGP Message Format" it is easy to spread EDS documents, keys and others.
For example a document, certified by EDS will be as following:
EDS document in "OpenPGP Message Format" stile.
-----BEGIN PGP SIGNED MESSAGE-----
information
-----BEGIN PGP SIGNATURE-----
sign
-----END PGP SIGNATURE-----
"OpenPGP Message Format" is widespread and is a standard for electronic mail coded messages.
Timestamps connection
The system such as Time marker service can exist only in case of real trust from user's side.
We use timestamps connection to increase the user's trust.
Timestamps forms series of stamps in which every subsequent stamp contains the evidence of being given after
the previous timestamp. (stamp contains the hash of the previous one)
Series of timestaps is a sequent of timestamps where every subsequent
stamp has the evidence of being given after the previous one.
The timestamp series are available for anyone to check its integrity.
If administrator tries to give timestamp with hind-sight,
the timestamp won't form the series of stamps. And an attempt of falsification will be detected.
Timestamp format
To provide everyone the possibility of checking the timestamp series,
service must have all the given timestamps and extend any of them on demand.
However timestamps contain some user's data.
This data can have a personal secret or just be too volumetric.
That is why timestamps kept on the server mustn't contain any open user's data,
so it's enough to keep only its hash.
Timestamp format published on the server. (is kept in DB)
-----BEGIN PGP SIGNED MESSAGE-----
Timestamp-version: (time marker format version)
Description: (short description of the message)
Signed-by: (URL of the service)
Timestamp: (Greenwich Time in RFC 822 format)
Number: (ordinal number of time marker)
Ref-Hash-SHA512: (SHA512 previous time marker's hash)
Ref-Hash-RIPEMD160: (RIPEMD160 previous time marker's hash)
Hash-SHA512: (SHA512 user's data hash)
Hash-RIPEMD160: (RIPEMD160 user's data hash)
-----BEGIN PGP SIGNATURE-----
sign in OpenPGP format
-----END PGP SIGNATURE-----
The connection between timestamps as well as between timestamp and
user's data is formed with two hash algorithms.
Note:
While calculating timestamp hash is counted not from all pgp file, but from necessary attributes only.