Command-line tool to create and verify OpenTimestamps proofs
Command-line tool to create and validate timestamp proofs with the OpenTimestamps protocol, using the Bitcoin blockchain as a timestamp notary. Additionally this package provides timestamping of PGP signed Git commits, and verification of timestamps for both Git commits as a whole, and individual files within a Git repository.
While OpenTimestamps can create timestamps without a local Bitcoin node, to verify timestamps you need a local Bitcoin Core node (a pruned node is fine).
Either via PyPi:
$ pip3 install opentimestamps-client
or from source:
$ python3 setup.py install
On Debian (Stretch) you can install the necessary system dependencies with:
sudo apt-get install python3 python3-dev python3-pip python3-setuptools python3-wheel
Creating a timestamp:
$ ots stamp README.md Submitting to remote calendar https://a.pool.opentimestamps.org Submitting to remote calendar https://b.pool.opentimestamps.org Submitting to remote calendar https://a.pool.eternitywall.com
You'll see that
README.md.ots has been created with the aid of three remote
calendars. We can't verify it immediately however:
$ ots verify README.md.ots Assuming target filename is 'README.md' Calendar https://alice.btc.calendar.opentimestamps.org: Pending confirmation in Bitcoin blockchain Calendar https://bob.btc.calendar.opentimestamps.org: Pending confirmation in Bitcoin blockchain Calendar https://finney.calendar.eternitywall.com: Pending confirmation in Bitcoin blockchain
It takes a few hours for the timestamp to get confirmed by the Bitcoin blockchain; we're not doing one transaction per timestamp.
However, the client does come with a number of example timestamps which you can try verifying immediately. Here's a complete timestamp that can be verified locally:
$ ots verify examples/hello-world.txt.ots Assuming target filename is 'examples/hello-world.txt' Success! Bitcoin block 358391 attests existence as of 2015-05-28 CEST
You can specify JSON-RPC credentials (
PASS) for a local bitcoin node like so:
$ ots --bitcoin-node http://USER:PASS@127.0.0.1:8332/ verify examples/hello-world.txt.ots Assuming target filename is 'examples/hello-world.txt' Success! Bitcoin block 358391 attests existence as of 2015-05-28 CEST
Incomplete timestamps are ones that require the assistance of a remote calendar to verify; the calendar provides the path to the Bitcoin block header:
$ ots verify examples/incomplete.txt.ots Assuming target filename is 'examples/incomplete.txt' Got 1 new attestation(s) from https://alice.btc.calendar.opentimestamps.org Success! Bitcoin block 428648 attests existence as of 2016-09-07 CEST
The client maintains a cache of timestamps it obtains from remote calendars, so if you verify the same file again it'll use the cache:
$ ots verify examples/incomplete.txt.ots Assuming target filename is 'examples/incomplete.txt' Got 1 attestation(s) from cache Success! Bitcoin block 428648 attests existence as of 2016-09-07 CEST
You can also upgrade an incomplete timestamp, which adds the path to the Bitcoin blockchain to the timestamp itself:
$ ots upgrade examples/incomplete.txt.ots Got 1 attestation(s) from cache Success! Timestamp is complete
Finally, you can get information on a timestamp, including the actual commitment operations and attestations in it:
$ ots info examples/two-calendars.txt.ots File sha256 hash: efaa174f68e59705757460f4f7d204bd2b535cfd194d9d945418732129404ddb Timestamp: append 839037eef449dec6dac322ca97347c45 sha256 -> append 6b4023b6edd3a0eeeb09e5d718723b9e sha256 prepend 57d46515 append eadd66b1688d5574 verify PendingAttestation('https://alice.btc.calendar.opentimestamps.org') -> append a3ad701ef9f10535a84968b5a99d8580 sha256 prepend 57d46516 append 647b90ea1b270a97 verify PendingAttestation('https://bob.btc.calendar.opentimestamps.org')
Timestamping and Verifying PGP Signed Git Commits
Timestamping inherently records potentially revealing metadata: the current
time. If you create multiple timestamps in close succession it's quite likely
that an adversary will be able to link those timestamps as related simply on
the basis of when they were created; if you make use of the timestamp multiple
files in one command functionality (
./ots stamp <file1> <file2> ... <fileN>)
most of the commitment operations in the timestamps themselves will be
identical, providing an adversary very strong evidence that the files were
timestamped by the same person. Finally, the REST API used to communicate with
remote calendars doesn't currently attempt to provide any privacy, although it
could be modified to do so in the future (e.g. with prefix filters).
File contents are protected with nonces: a remote calendar learns nothing about the contents of anything you timestamp as it only ever receives an opaque and meaningless digest. Equally, if multiple files are timestamped at once, each file is protected by an individual nonce; the timestamp for one file reveals nothing about the contents of another file timestamped at the same time.
OpenTimestamps is alpha software, so it's possible that timestamp formats may have to change in the future in non-backward-compatible ways. However it will almost certainly be possible to write conversion tools for any non-backwards-compatible changes.
It's very likely that the REST protocol used to communicate with remote calendars will change, including in backwards incompatible ways. If this happens you'll just need to upgrade your client; existing timestamps will be unaffected.
As a short-term measure, the raw calendar data for the three calendar servers
in operation at this time can be downloaded directly. See
contrib/calendar-mirror.sh script for details.
Use the setuptools development mode:
python3 setup.py develop --user
Need unit tests for the client.
Git tree re-hashing support fails on certain filenames with invalid unicode encodings; this appears to be due to bugs in the underlying GitPython library. As a work-around, you may find the
convmvtool useful to find and rename these files.
Git annex support only works with the SHA256 and SHA256E backends.
Errors in the Bitcoin RPC communication aren't handled in a user-friendly way.
Not all Python platforms check SSL certificates correctly. This means that on some platforms, it would be possible for a MITM attacker to intercept HTTPS connections to remote calendars. That said, it shouldn't be possible for such an attacker to do anything worse than give us a timestamp that fails validation, an easily fixed problem.
ots-git-gpg-wrapper doesn't yet check for you if the timestamp on the git commit makes sense.
bitcoinpackage can cause issues, with ots confusing it with the required
python-bitcoinlibpackage. A symptom of this issue is the message
AttributeError: module 'bitcoin' has no attribute 'SelectParams'or
JSONDecodeError("Expecting value", s, err.value) from None. To remedy this issue, one must do the following:
# uninstall the packages through pip pip3 uninstall bitcoin python-bitcoinlib # remove the bitcoin directory manually from your dist-packages folder rm -rf /usr/local/lib/python3.5/dist-packages/bitcoin # reinstall the required package pip3 install python-bitcoinlib
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