The fourth amendment to the US constitution protects people from seizures and searches in certain situations for reasons of privacy.

In Katz v United States, the US Supreme Court has defined a two-part test on whether a search violates a person's right to privacy:

  • The person must have had an expectation of privacy
  • The expectation must be reasonable

When a person sends a letter, the contents of the letter are protected by the Fourth Amendment, because the letter is sealed.

When a person sends data on the Internet, would the same argument hold?

This question is asked in the light of recent attempts to force companies to create backdoors in encryption, so that they can decrypt data when requested to do so.

  • interesting question, but possibly mute. The FISA, USA freedom act, and similar laws on US spying all seem to make it clear that United State citizens and people within the US are pretty strictly protected, It's the non-united state citizens that the government is allowed to spy on with every shady trick they can think of, such as backdoors. Since the fourth amendment only applies to those citizens protected in the above acts the government wouldn't be authorized to exploit any backdoors around encryption on anyone that could claim a fourth amendment right to privacy.
    – dsollen
    Commented Jan 6, 2016 at 7:36
  • Actually, now that I think of it the Computer Fraud and Abuse Act is very open ended, arguably too much so since people have been tried for breaking it just for accidentally stumbling upon a software bug and reporting it. It's possible trying to use any information received from a secured connection would be seen as illegally obtained to violating the CFAA
    – dsollen
    Commented Jan 6, 2016 at 7:38

1 Answer 1


I don't think any appellate court has given an opinion on whether encryption creates a reasonable expectation of privacy. This is not surprising as only recently has it come to light that the government may have weakened encryption protocols and asked for backdoors in order to aid in decryption.

However, Orin Kerr, professor of Law at George Washington University School of Law wrote this article in 2001. He argues that encryption does not create a reasonable expectation of privacy.

He says:

the Fourth Amendment regulates access, not understanding.

Once you introduce your communication into third party systems (or the garbage :P), they may give it up to the government. If the government happens to be able to understand that communication, so be it.

He shows how this conclusion is consistent with how the courts have ruled on "reassembly of shredded documents, recovery of deleted files, and the translation of foreign languages".

Note that the reasonable expectation of privacy test is only one of the tests used to determine whether a search or seizure is reasonable. Another test is the "trespass" test which deems an interaction to be a search per se if there is a trespass on a person's personal effects. It was used before Katz and was reiterated recently in US v Jones (2012). Regardless, your question is still meaningful because the two tests are used alongside each other.

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