The International Chemical Identifier (InChI) is a textual identifier for chemical substances, designed to provide a standard way to encode molecular information and to facilitate the search for such information in databases and on the web. It is maintained by the InChi Trust.
InChI and InChIKey are open standards. They use unique machine readable strings to represent, store and search chemical structures. All the software and algorithms related to them are open source and is now on GitHub.
https://github.com/IUPAC-InChI/InChI
The new version can be tested with a web demo version (https://iupac-inchi.github.io/InChI-Web-Demo/) which allows users to draw a chemical structure and calculate the InChI; this works in the browser, so no data is shared with external servers.
