[brlewis]

In theory, a mathematical formula is not patentable. In theory, a patent that precludes every practical use of a mathematical formula is invalid. In theory, a patent is required to be specific enough that a person of ordinary skill in the field could use it to reduce the invention to practice (a requirement that no homomorphic encryption patent could possibly meet.)

By "theory" I mean statute and Supreme Court precedent. These are just theory, not law. Law is not what the legislature says or what the Supreme Court says. Law is what happens to you in court.