Public providers

There are several timestamping services around. Here is a list of publicly available services you can try:

• http://freetsa.org/tsr

• http://time.certum.pl

• http://timestamp.comodoca.com/rfc3161

• http://timestamp.geotrust.com/tsa

• http://timestamp.globalsign.com/scripts/timstamp.dll

• http://tsa.starfieldtech.com

• https://teszt.e-szigno.hu:440/tsa

Example

>>> import rfc3161ng
>>> certificate = open('data/certum_certificate.crt', 'rb').read()
>>> rt = rfc3161ng.RemoteTimestamper('http://time.certum.pl', certificate=certificate)
>>> tst = rt.timestamp(data=b'John Doe')
>>> rt.check(tst, data=b'John Doe')
True
>>> rfc3161ng.get_timestamp(tst)
datetime.datetime(2017, 8, 31, 15, 42, 58, tzinfo=tzutc())

Example for a server that insist on SHA256:

>> import rfc3161ng >> timestamper = rfc3161ng.RemoteTimestamper(’https://interop.redwax.eu/test/timestamp’, hashname=’sha256’) >> tsr = timestamper(data=b’The RedWax Project’, return_tsr=True) >> print(‘{}’.format(tsr))

Verifying timestamp using OpenSSL

One can verify the timestamp returned by the timeserver by using OpenSSL. For example with:

$ openssl ts -verify -data data_file.txt -in data_file.tsr -CAfile cacert.pem -untrusted tsa.crt

To save the tsr you can use code similar to:

>>> from pyasn1.codec.der import encoder
>>> import rfc3161ng
>>> ...
>>> timestamper = rfc3161ng.RemoteTimestamper('http://freetsa.org/tsr', certificate=certificate_data)
>>> tsr = timestamper(data=data_file.read(), return_tsr=True)
>>> with open("data_file.tsr", "wb") as f:
>>>     f.write(encoder.encode(tsr))

Alternatively you can just save the raw response.content returned from the certification server.

There is a test which also covers this in test_verify_timestamp_response_with_openssl.

Authors

• Benjamin Dauvergne <bdauvergne@entrouvert.com>

• Michael Gebetsroither <michael@mgeb.org>

• Bas van Oostveen <trbs@trbs.net>