[kichik]

Not exactly the point of this article, but it would be cool if APIs like this can return the expected signed string for debugging. It would have to be properly limited for security. But if the API is expecting non-standard signatures, it could help developers with better debugging tools.

[lillesvin]

Given that you can't infer the error from simply looking at the signature string, I don't see how having the expected string rather than a simple "OK" or "mismatched signature" (as you get now) would make a difference?

[kichik]

You can save the expected string to a file, save your string to a file, and run diff on a hexdump of both. Even without hexdump, you should see the difference between "\n" and "\\n" in properly escaped output.