Self-defense is an interesting approach to privacy.
So far, we've been treating encryption as a matter of privacy (Fourth Amendment). But since the U.S. government has historically treated encryption as a weapon, perhaps we could also argue that encryption is a matter of the Second Amendment. It would be really interesting to get the NRA, Rand Paul, and Bernie Sanders to speak out in favor of encryption at the same time...
Of course, the flip side of this approach is that it's much easier to support restrictions on the possession, use, and export of weapons. "Export-grade" ciphers are still causing issues 20 years later.
And just for the hell of it, let's throw in the (nearly-never cited) 3rd Amendment.
It "places restrictions on the quartering of soldiers in private homes without the owner's consent". This explicitly was to prevent citizens from having to bear the capital costs associated with the government's own decisions, but it also appears to have been borne out of a fear of having a government agent be able to observe one's most private affairs.
For better or worse, the 3rd amendment doesn't come with the precedents of the 2nd or 4th. There is an argument to be made that by having a General of the US Military capable of monitoring me while sitting on my couch (in a realistic scenario via my cell phone or Xbone), that the military is overstepping its constitutional bounds with respect to my privacy. This would not apply so much to the FBI, but it might eventually were precedent to be pushed in the correct direction.
The part about "prevent[ing] citizens from having to bear the capital costs associated with the government's own decisions" is also interesting.
It could mean that if the Feds want to make their own jobs easier by trespassing on the private property (laptops, phones, etc.) of citizens, they'll have to get the owner's permission first.
Now that we've successfully reinterpreted the 2nd, 3rd, and 4th Amendments to support privacy, why not the 1st Amendment? Would you like to join the Church of Privacy and accept Ed Snowden as your Lord and Savior? According to our Holy Book, in order to reach salvation, you must vigorously resist the Devil's attempts to spy on your life. Oh, and the 5th already gives you the right to refuse to divulge encryption keys, at least on some interpretations.
So far, we've been treating encryption as a matter of privacy (Fourth Amendment). But since the U.S. government has historically treated encryption as a weapon, perhaps we could also argue that encryption is a matter of the Second Amendment. It would be really interesting to get the NRA, Rand Paul, and Bernie Sanders to speak out in favor of encryption at the same time...
Of course, the flip side of this approach is that it's much easier to support restrictions on the possession, use, and export of weapons. "Export-grade" ciphers are still causing issues 20 years later.