Request-a-copy: ALTCHA challenge endpoint doc

captcha.md

@@ -0,0 +1,41 @@
+# Captcha Endpoints
+[Back to the list of all defined endpoints](endpoints.md)
+
+## Main Endpoint
+**/api/captcha**   
+
+Not allowed. At this time, only the `challenge` endpoint is available.
+
+## Retrieve a challenge from the (ALTCHA) captcha service
+**/api/captcha/challenge**
+
+If the captcha provider is enabled and configured to be 'altcha', this endpoint will return a challenge for the browser to complete as proof-of-work.
+
+This is not an addressable HATEOAS object, or endpoint, but rather a JSON object that is meant to be consumed and processed in the browser.
+
+The JSON body will contain the algorithm, salt, signature, and challenge. An example is below:
+
+```json
+{
+  "algorithm": "SHA-25", 
+  "salt": "dcf5eba26e",
+  "challenge": "0d8dd34089fdd610bd9a8857ea1fa4a5f9fe4b53f5df0c4e1eff6dc987c4d2bf",
+  "signature": "dfe4ec56f3d61e3a021b1c3b3ea4c7d6aea9812ab719ffe130fd386ce0b4158c"
+}
+```
+
+An example curl call:
+```
+curl -i https://demo.dspace.org/server/api/captcha/challenge
+```
+
+For more information about ALTCHA challenge creation, see: https://altcha.org/api/operations/createchallenge/
+
+The final result of the work is not submitted to this endpoint, but instead included with form data submitted in the captcha-protected form, for final verification and validation.
+
+This endpoint does not relate to Google ReCaptcha, which calls 3rd party services directly from the frontend for captcha validation)
+
+Return codes:
+200 OK - if the operation succeeded and the JSON body is returned
+400 Bad Request - if the captcha provider is not enabled or configured to be 'altcha', or the algorithm is not supported
+500 Internal Server Error - if the challenge or hmac hash cannot be calculated

endpoints.md

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 * [/api/authn/login](authentication.md#Login)
 * [/api/authn/logout](authentication.md#Logout)
 * [/api/authn/status](authentication.md#Status)
+* [/api/captcha/challenge](captcha.md)
 * [/api/config/harvestermetadata](harvestermetadata.md)
 * [/api/config/submissiondefinitions](submissiondefinitions.md)
 * [/api/config/submissionsections](submissionsections.md)