US Patent 11258599 Stable physically unclonable function

A system and method use a physical unclonable function in a PUF circuit on an integrated circuit to generate a security key, and stabilize the security key by storage in a set of nonvolatile memory cells. The stabilized security key is moved from the set of nonvolatile memory cells to a cache memory, and utilized as stored in the cache memory in a security protocol. Also, data transfer from the PUF circuit to the set of nonvolatile memory cells can be disabled after using the PUF circuit to produce the security key, at a safe time, such as after the security key has been moved from the set of nonvolatile memory cells to the cache memory.