That's quite cute, although the first thing I do when confronted with a blank page is highlight it ( I don't know why). If you had the encryption tools to sign a message then you probably have the tools to encrypt it too, which is the best kind of 'hidden message'.

I can see how you could get away with it by writing a message where you tell a joke and then "scroll down to read the punchline", and put your program in the scroll down bit.

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Jeremy
I didn't believe in evil until I dated it.