Couldn't find existing issue so I decide to create new one. I just quote beginning of issue found on ubercart.org site.
I'm testing our ubercart module and I can't seem to get to the review page. Every time I hit the check out button and the button of the page I get this error "To protect our customers from identity theft, credit card details are erased when a browser refreshes on the checkout review page. Please enter your card details again and re-submit the form." (...)
The problem basically occur when you accidentally leave new line (or whatever whitespace / tab/ newline/ etc.) on the end (or in the beginning) in your uc_credit.key secret file. It's really hard to spot and system doesn't give any useful information except misleading above message: "To protect our customers from ...".
So my solution is simple just trim() every whitespace from the beginning and end of the key, after loading.
Patch in attachment.
PASSED: [[SimpleTest]]: [MySQL] 1,917 pass(es).
PASSED: [[SimpleTest]]: [MySQL] 2,453 pass(es).
PASSED: [[SimpleTest]]: [MySQL] 1,908 pass(es).