[xorcist]

The first cat does absolutely nothing in your example.

[pmarreck]

are you sure? how else would you pipe to GPG?

[yuubi]

Just redirect gpg's input from the file?

    gpg ... < hello.txt | curl ...

Its stdin will be the file instead of a pipe, but few programs care about the difference and fewer still in such a way that you'd prefer to use the pipe.