Just because the Constitution does not exclusively enumerate rights does not mean any particular right not enumerated exists. In English law, "rights" arose from law and tradition. It's a fundamentally backward-looking analysis, not a forward-looking one.

Do you have the right to use strong encryption? If you can fit it into a right the framers would have recognized based on English law and tradition (probably free speech), then yes. If not, then no. The 10th amendment has nothing to say about that.

Fundamentally, the Constitution is not really about "rights." The Bill of Rights was added to appease those who were worried the central government would impinge on the traditional rights of Englishmen. But the real purpose of the exercise was to create a powerful, but democratic, central government that had the authority to do the things that needed to be done.

Was the Constitution always interpreted that way? Was it written by people who thought that way? The assertion that the Xth Amendment is a nullity seems to indicate a shift in the way the Constitution fits in law. Or at least it indicates that the interaction between deference to that document and the way US law evolved turned some words that people who wrote them thought meant something into a nullity.

Many people at the time thought the 10th amendment was superfluous: http://tenthamendmentcenter.com/2013/03/05/a-brief-history-o....

To be precise, the 10th amendment is a nullity if you already accept that the federal government is one of enumerated powers. At the time of the founding, that was a novel concept and it probably made some people feel better to have it stated explicitly. But today that's taken as a given. The debate is never over if the government has powers not enumerated, but whether a particular action falls within the scope of an enumerated power. And the 10th amendment tells you nothing about the scope of the enumerated powers.