re: statue of limitations - if we are talking exponential levels of difficulty to crack vs. exponential increases in computing power (Moore's law) I wonder whether "we won't have the computing power to crack this for X years, so a statute of limitations of (X-1) years to solve this means that we are functionally unable to answer the question within the allotted time" becomes defensible as a reason to call something "impossible", i.e. it's improbable to solve during the statue of limitations
Statue of limitations is only until the court date. Once that starts there is no statue of limitations, even if the case takes years.
The closest I can think of is a right to a speedy trial, but that has so many exceptions (for example if the person is out on bail) that I couldn't say how a judge would rule in this scenario. Especially if it was the defendant causing the delay by refusing to reveal the password and making the prosecutor get it the hard way. (Not applicable in this case, might be applicable in another.)
specifically in this case, the only non-John Doe defendant I am aware of is dead so those provisions do not apply.
The FBI is not doing this for proceedings related evidenciary purposes but instead for investigative purposes. No one has been charged here (from what I know) so the issue of speedy trials is moot while the statue of limitations on the crimes under investigation are likely extremely long if they exist at all.
A statute of limitations prevents you from charging someone with a crime once some period of time elapses. It says nothing about how long you have to prove your case in court. That's more likely to run afoul of the right to a speedy trial.
