Trusted Timestamps - understanding the format (rfc3161)

Question

[edit: I've written a blogpost that explains everything in detail: look here]

Hi!

I'm desperately trying to build a service for trusted timestamps based on rfc3161. I've decided to use the free trusted timestamp service at zeitstempel.dfn.de.

My question is how i shall contact this service in order to receive a valid response. Regarding the request format, the RFC tells:

TimeStampReq ::= SEQUENCE  {
   version                      INTEGER  { v1(1) },
   messageImprint               MessageImprint,
     --a hash algorithm OID and the hash value of the data to be

     --time-stamped
   reqPolicy             TSAPolicyId              OPTIONAL,
   nonce                 INTEGER                  OPTIONAL,
   certReq               BOOLEAN                  DEFAULT FALSE,
   extensions            [0] IMPLICIT Extensions  OPTIONAL  }

where

   MessageImprint ::= SEQUENCE  {
        hashAlgorithm                AlgorithmIdentifier,
        hashedMessage                OCTET STRING  }

I've found a client which helped me a bit.

Nevertheless, I still don't know how I should construct the request for the timestamp service.

Regards!

Answer 1

I'm glad that you find our software helpful. But you refer to our old service. Please visit www.ntp.org.pl - you'll find there the latest version of timestamping client and a lot of other useful free software related to time topic.

I'm not sure what you want to do. Maybe if you give a few more details, I'd be able to help you better. Anyway, I'll give you some hints, where to find some precious information.

Firs of all, you should look at OpenSSL project: http://www.openssl.org/docs/apps/ts.html# There is an example, how to create TSRequest. The request is stored in file, so you can read it's content. Later, you can send request to the server using this: http://www.openssl.org/docs/apps/tsget.html#

Antoher trick you can do is to install some sniffer (for example Wireshark - www.wireshark.org/ ), start our client from www.ntp.org.pl , send request, then find proper packet in wireshark to see what it contains.

Feel free to ask, if you have some additional questions. Please, give some more information about your service.