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tsp-client: An IETF Time-Stamp Protocol (TSP) (RFC 3161) client

tsp-client is an implementation of the RFC 3161 TSP protocol in Python.

TSP is used for point-in-time attestation and non-repudiation as part of various electronic signature and code signing schemes, including eIDAS XAdES (tsp-client is used by SignXML to implement XAdES).

Installation

pip install tsp-client

Synopsis

from tsp_client import TSPSigner, TSPVerifier

# Sign a message online by transmitting its digest to the timestamp authority
message = b"abc"
signer = TSPSigner()
signed = signer.sign(message)  # Returns raw bytes of the verified timestamp token.

# Verify a presented timestamp token offline using the original message
verified = TSPVerifier().verify(signed, message=message)

# Or sign and verify using the message digest (digest algorithm may vary)
import hashlib

digest = hashlib.sha512(message).digest()

signer.sign(message_digest=digest)
verified = TSPVerifier().verify(signed, message_digest=digest)

print(verified.tst_info)  # Parsed TSTInfo (CMS SignedData) structure
print(verified.signed_attrs)  # Parsed CMS SignedAttributes structure

Specifying a custom TSA

To provide a timestamped signature with non-repudiation verifiable via a chain of trust, TSP requires the use of a TSA (time-stamp authority) server when generating timestamp tokens. TSA servers can be thought of as digital notaries. Verification of tokens can be done offline using your system's certificate authority (CA) trust store.

By default, tsp-client uses the DigiCert TSA server when signing tokens. To use a different TSA, set the SigningSettings.tsp_server attribute as follows:

from tsp_client import TSPSigner, TSPVerifier, SigningSettings
signing_settings = SigningSettings(tsp_server="http://timestamp.identrust.com")
signer = TSPSigner()
signed = signer.sign(message, signing_settings=signing_settings)

There is currently no credible public TSA that offers HTTPS transport security and does not apply throttling. DigiCert provides a relatively high throughput public TSA endpoint, but your message digests and tokens will be transmitted unencrypted over the network. As an alternative, Sectigo offers an HTTPS TSA (https://timestamp.sectigo.com) but applies throttling so is only suitable for low throughput applications.

The European Union maintains a list of trusted TSAs as part of the eIDAS dashboard, however this list only serves as a root of trust and does not link directly to the TSA endpoints of listed providers.

Authors

  • Andrey Kislyuk

Links

Bugs

Please report bugs, issues, feature requests, etc. on GitHub.

License

Copyright 2022-2023, Andrey Kislyuk and tsp-client contributors. Licensed under the terms of the Apache License, Version 2.0. Distribution of the LICENSE and NOTICE files with source copies of this package and derivative works is REQUIRED as specified by the Apache License.