Especially errors with calculation of secrets, should benefit from the descriptions of http://developers-hyves.nl/documentation/data-api/content-encoding. If you have problems with secrets, please check our http://developers-hyves.nl/documentation/data-api/oauth-example-code, and see if your code behaves the same way for each example. The examples were taken from http://wiki.oauth.net/TestCases, and most of them serve as unit tests for us.

Another problem that we encountered, is that PHP (or the browser?) translates http://data.hyves-api.nl to http://data.hyves-api.nl/ (note the final slash). If the Consumer calculates the oauth_secret on the basis of an URI without the final slash, and the Service Provider does include the final slash, the secrets will not match. So make sure that you always have your URI end in a slash.

You can use debugging oauth signature calculation.