Intermingling signatures or authentication and data layout is such a common failure and people do it over and over again, even in relatively new projects like A

Intermingling signatures or authentication and data layout is such a common failure and people do it over and over again, even in relatively new projects like Android. I wonder why the initial design took off? This is something were I would expect any crypto engineer to refuse to sign the design off, because it is going to break; it's not even a question. If you do anything other than Sign(Blob) and later Verify(Signature, Blob) && Parse(Blob) you're going to do it wrong.