The issue of malicious hackers is not separate from the issue of warrant compliance. Whatever system you use to comply with warrants is a system that can and w

The issue of malicious hackers is not separate from the issue of warrant compliance. Whatever system you use to comply with warrants is a system that can and will be attacked. This was widely discussed in the 90s during the push for key escrow and key recovery systems. Secret sharing makes sense, but not in the context of a system like Lavabit. Where secret sharing makes sense is in identity based encryption, which is similar to Lavabit in that keys are generated by a trusted authority, but is different in that the authority does not store keys or decrypt messages. Threshold IBE is useful in settings where there are multiple key generation authorities, which must jointly compute secret keys from their shares of the master secret. Finally, I would not rely on anyone to shut their service down in the name of fighting an overly broad warrant. First, whether or not a warrant is too broad is a matter of opinion, and the service operator's opinion may differ from my own. Second and more disturbing, there is no guarantee that the service operator can legally shut the service down when such a warrant is received. As I said elsewhere, Lavabit's users are lucky that the founder was willing to take a stand like this; it is not something I would expect.