IEEE Electrification - March 2021 - 67

use of a cryptographic algorithm, e.g., the Advanced
Encryption Standard (AES). For a symmetric key cryptographic system like AES, a key is used to encrypt the data,
and only the person who has the same key can decrypt
the received ciphertext (Figure 1). It, therefore, requires
that the keys distributed to two parties have to be generated securely, i.e., unknown to attackers.
This secure key exchange process is achieved by a key
generation system, e.g., public key cryptographic methods
such as the Diffie-Hellman key exchange (DH) and Rivest-
Shamir-Adleman (RSA). The security of DH is guaranteed
based on the computational difficulty that the discrete
logarithm problem cannot be efficiently solved, and the
security of RSA rests on the notion that factoring a product of two large prime numbers is difficult to solve. In fact,
all of the classical public key systems rely on mathematical assumptions, i.e., a certain mathematical problem cannot be efficiently solved even by the most powerful
modern supercomputer using any existing algorithm.
Once there is a way to efficiently address those mathematical problems, the existing microgrid communication
systems will no longer be secure.

a quantum computer with 1,000-plus qubits targeted for
the end of 2023. As the U.S. Department of Energy
announced in August 2020, it has decided to allocate
US$625 million in funds to support multidisciplinary quantum information science research, especially quantum
computing, over the next five years. Note that although the
occurrence of quantum computers strong enough to break
current cryptographic systems is perhaps still far away, the
high risk is forthcoming.

Quantum Communication for Microgrids
Unlike classical communication that relies on mathematical assumptions, quantum communication is based on
the fundamental laws of quantum physics, which provide
a more solid foundation in the quantum era as they have
been fairly heavily tested. In this section, we first present
an overview of quantum cryptography techniques offering
some promising candidates for securing microgrids and
then introduce some basics of the most mature technique
in quantum cryptography, namely quantum key distribution (QKD). We then report some existing designs of QKDbased microgrid and networked microgrids (NMs)
communication architectures.

The Quantum Era Is Coming
These mathematical problems, while they are hard to
An Overview of Quantum Cryptography
A potent solution to tackle the threat posed by quantum
solve with modern computers, are at risk of being
computers is using quantum cryptography, which exploits
addressed by quantum computers. Quantum computing
the principles of quantum mechanics to perform cryptoexploits quantum-mechanical properties such as supergraphic tasks such as encryption and decryption, authentiposition and entanglement to offer the probability of
cation, and key distribution. A number of quantum
improving the computational capability. Since 1982, when
cryptography techniques have been proposed in the literaa quantum machine was envisioned by Richard Feynman
ture. The most well-known and mature one to date is QKD,
to simulate quantum physics, tremendous progress has
the performance of which has been demonstrated in labobeen made on developing quantum computing hardware
ratories and relevant real-world applications such as comand algorithms. In the early 1990s, Dr. Peter Shor presentputer networks, online banking, private clouds, and critical
ed an algorithm, now well known as " Shor's Algorithm, "
infrastructures for government and industry. Beyond the
that was able to effectively factor a product of two large
realm of QKD, some other quantum cryptography techprime numbers with the help of a quantum computer
niques exist, including quantum random number generaequipped with enough stable qubits, thus defeating the
tion, quantum coin flipping, quantum money, quantum bit
RSA encryption algorithm.
commitment, and position-based quantum cryptography.
Today, quantum computing has been a hot and strateThese all utilize quantum information in different cryptoggic research area among academia, government, and
raphy scenarios, e.g., the uncloneable money.
industry, including big companies like Google, IBM, MicroHowever, although a variety of quantum cryptography
soft, Intel, Alibaba, and many more, that are actively purtechniques exist, their applications in microgrids have not
suing the goal of developing the first large-scale universal
yet been extensively investigated. An important reason for
quantum computer. Google reported in 2019 that a quantum computer with 53 qubits was
able to achieve quantum supremacy over certain problems. In August
Secret Key k
2020, Google announced another
big breakthrough by performing the
Party B
Party A
largest chemical simulation on a
Ciphertext Ek (m )
Plaintext m
Plaintext m
quantum computer.
Decryption
Encryption
IBM, another strong competitor
in quantum computing, released a
roadmap in September 2020 indicat- Figure 1. An illustration of a symmetric-key cryptographic system, where a single key is used for
ing that the IBM team is developing encryption and decryption. m: message; Ek(m): encrypted key message.

IEEE Electrific ation Magazine / MARCH 2 0 2 1

IEEE Electrification - March 2021

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