README

git-certify is a script for git that can be used to automate the publication
of proof of existence of git commits using blockchain technology.

To do so we create a special bitcoin transaction using bitcoin opcode OP_RETURN.
OP_RETURN instantly mark a transaction as unspendable. It's output can hence be
pruned from the blockchain database by nodes who need space without
compromising their database coherency. The OP_RETURN opcode also allows up to
80 bytes of data to be embedded in the transaction output. We use this space to
store the git hash and a marker ('git:') to identify the type of message.

Once the transaction is mined in a bitcoin block, it can be proved the git
commit and all commits and files that makes the branch up to the certified commit
existed at the time the block was mined.

You can watch special transactions in bitcoin mainnet and testnet at: http://coinsecrets.org/

Usage
-----
Run bitcoind as a rpc server

Add git-certify in your PATH:
export PATH=$PATH:path_to_git-certify

Then, from your git project:
git certify HEAD

Requirements
------------
python-bitcoinlib:
pip install python-bitcoinlib

bitcoind running as a rpc server

Please note:
THIS SOFTWARE IS PROVIDED BY JOSSELIN COSTANZI AND CONTRIBUTORS ``AS IS'' AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL JOSSELIN COSTANZI AND CONTRIBUTORS BE LIABLE FOR
ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.