Self-hosted vs Sentinel vs SaaS API

When the using self-hosted integration, the ALTCHA challenge is generated & and verified directly on the drupal instance. It works out of the box with the module and has no external dependencies.

When using the Sentinel integration, the challenge is generated and verified by the Sentinel service. This adds a layer of protection on top of the default proof-of-work mechanism of ALTCHA. Important: there is no SaaS solution for Sentinel, and it needs to be set up and hosted manually. More info on the exact features and setup can be found here.

When using SaaS integration (deprecated), the challenge is fetched from the ALTCHA API instead. For this to work, an API key with the Antispam API feature is required. More info on API keys can be found here.