Page 74 - Cyber Warnings

to make a copy of an unknown quantum state. A quantum system can be entangled with only
one quantum system and, with the definition of entanglement being the only thing we know
about paired qubits is that they are opposite, the paired systems are not clones. The reverse of
the no-cloning theorem is the no-delete theorem which states that given an entangled quantum
state it is impossible to delete one of the copies. The no-teleportation theorem explains that a
quantum state cannot be converted into classical bits, ones and zeros.

This relates to the Kochen-Specker theorem which says it is impossible to add values to
physical observables meaning that even with an infinite number of classical bits you could not
fully describe the state of a quantum system. The no-broadcast theorem branches off of the no-
cloning theorem. Quantum information cannot be copied so there cannot be more than two
recipients, both sides of the entangled system, for there to be more than two sides that means
the information has to be copied in some way. Quantum mechanics having these theorems
make for a very safe and efficient type of encryption. It also makes it possible to detect eaves
dropping easily because if a quantum state is observed then it changes that very data, which
would alert both sides that someone has tampered with the quantum information.

Quantum key distribution, which makes use of all the theorems above, is the only encryption
system provably secure by the laws of physics. It uses quantum mechanics to produce a shared
random secret key which is only known to each party. The randomly generated quantum key is
sent through a fiber optic line as a photon. Information, previously encrypted with that key, is
sent over the internet to the intended recipient and the only way to encrypt that data is with the
quantum key sent across the fiber line. If information through the internet is copied it is not
possible to decrypt it because a man in the middle cannot recreate the quantum state of the
private key. If the private key is observed through a man in the middle attack on the fiber optic
line it changes since it was observed and once it ends up at its intended destination the receiver
of the private key can see that it was observed due to the quantum state having changed. There
is a physical limitation to this system, fiber optic lines for quantum key distribution have a
maximum length of 60 miles. For this to work successfully, trusted quantum key distributors
must be set up every 60 miles in a web shape to cover a wide area.

The quantum age is rapidly approaching making it necessary to adapt our computers to be able
to withstand a brute force attack pushing us to stray away from our current factorization-based
encryption and adopt new methods like hidden Goppa code, random strings, and multilayered
polynomial schemes. The development of current quantum computers, spearheaded by the
company D-Wave who is backed by major companies such as Google, Lockheed Martin, and
NASA, has passed the “is it possible?” stage and is now moving into the “is it scalable?” stage.
The largest current quantum computer is the D-Wave 2000Q which contains 2000 qubits. This
n
computer based on the equation of transferring quantum bits into classical bits (2 = X) and
using 2000 for “n,” shows that “X” is essentially an infinite number of bits. Due to this, the future
of information security is progressing in the direction of quantum key distribution as it is the only
encryption scheme provably secure by the laws of physics.

74 Cyber Warnings E-Magazine – June 2017 Edition
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