I wrote "is deliberately encrypting and refusing to provide access to those books obstruction?". And again, I don't think that argument is anywhere near as clear cut as you want it to be. The fifth amendment, again, is intended to prevent torture, not to prevent the collection of evidence in a criminal investigation.
So technicalities like you're invoking (is refusing to do something "obstruction" or not?) need to be balanced against technicalities on the other side (is providing a decryption key "testimony"?). And when courts have had to make decisions like this they've almost always done it by splitting the difference in some way instead of finding an absolute interpretation on one side or the other.
Oh, after the fact? I would agree that is definitely obstruction. Before the fact - maybe for business, but not for personal. 5th amendment is to protect against forcing someone to provide evidence against themselves whether that is through torture or coercion, it does not matter.
But again you face the technicality: is providing access to already-existing documents "testimony" in the sense the fifth amendment intends? You can't torture someone into producing documents that don't exist, obviously! Nor is going to jail for obstruction of justice "coercion", effectively by definition.
I'm not saying I disagree with you in principle, I'm saying that very reasonable courts might not. This isn't a cut and dry argument, at all.
So technicalities like you're invoking (is refusing to do something "obstruction" or not?) need to be balanced against technicalities on the other side (is providing a decryption key "testimony"?). And when courts have had to make decisions like this they've almost always done it by splitting the difference in some way instead of finding an absolute interpretation on one side or the other.