This doesn't seem to work. Compiled from source on macOS Sierra 10.12.2. I tried a valid JWT and it reports back instantly that the key is 'e'. Also does the same with invalid JWT.
The JWT example in the readme works, but another valid JWT does not. Ubuntu 16.04.
That is definitely strange, if it is not sensitive data, would you mind sharing the JWT and the original secret? or try to find another example where it behaves like this?
Thanks
It is sensitive data so I can't share the payload for a (possibly unfounded) fear of brute-forcing the correct key used. I can tell you that the key is not an ASCII string (it is a random sequence of bits). The jwt.io debugger verified the signature when I gave it the proper key and failed to verify with the key "e" that this tool reported.