That conclusion is similar to the concept of 'unconditional security' especially WRT one-time pads. The key must be at least as long as the message itself. Oth

That conclusion is similar to the concept of 'unconditional security' especially WRT one-time pads. The key must be at least as long as the message itself. Other forms of encryption are based on assumptions and conditions being true (e.g. factoring is a hard problem, etc.) that may or may not be true. We don't know.