Quantum permutation pad for universal quantum-safe cryptography

Classical cryptographic techniques are currently under the growing quantum computing threat. New techniques that quantum computing algorithms cannot break are urgently needed. We present such an encryption method. It builds upon quantum permutation logic gates or quantum permutation pads. It is universal in that it can be equally employed on classical computers, today's Internet, and the upcoming quantum Internet. While the cryptographic technique is formulated in a quantum computing framework, it does not rely on physical properties uniquely present at the quantum level, such as no-cloning or entanglement of data. It achieves with today's technology a level of security comparable to what will be possible to attain with tomorrow's quantum technology. The mathematics behind the cryptographic technique, quantum representations of a symmetric group over a computational basis, is surprisingly simple. However, the challenge faced by an adversary wishing to break the code is intractable and uninterpretable, a property of Shannon's perfect secrecy. We believe that the cryptographic technique presented in this article can be used in several different ways and modes. It can be integrated into numerous current Internet protocols, or the Internet of Things, making them quantum safe. In addition, it can be used to transition to the upcoming Internet quantum technology smoothly.