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@2) Wouldn't it be possible to reverse engineer a military receiver? Or is it a changing passcode that must be input manually?

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I don't know much about the cryptology they use, but I do know that the keys are time-limited and I'm pretty confident the encryption is strong.

* If you steal a key, it will stop working after a brief time (probably hours to days).

* Knowing the decryption key does not (necessarily) mean you can perform the encryption.

http://en.wikipedia.org/wiki/Public-key_cryptography

Yeah, but that doesn't help if you have the device which decrypts the signal. Then you should be able to get the key (which would probably still be fairly difficult).

A receiver/decrypter only contains the public key, which can't be used to encrypt a new message. Perhaps you aren't familiar with asymmetric / public key cryptography?

And that is one reason the US military spends so much money and effort on anti-tamper[1] design and technology.

[1] http://www.at.dod.afrl.hpc.mil/

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