# [PERSON] on Korean Block Ciphers
## 1 Introduction  
As the Internet of Things (IoT) technology gets developed, a number of wearable and smart devices are gradually spreading through people's life [1]. Between these IoT devices, abundant data, from simple sensor data to even sensitive personal data, are being exchanged and processed. In order to protect these sensitive data, the exchange process of the data must be secured properly. To achieve the security, cryptographic algorithms must be applied to the data. However, applying the cryptographic algorithm requires resources, including computational power and memory. Most of the IoT devices do not have enough resources in order to apply cryptographic algorithms of conventional computers since most of them are equipped with low computational power and small memory footprint.  
In order to resolve this hard condition, lightweight cryptography has been actively studied [2]. Unlike classical cryptography, a lightweight cryptography is designed for low-end devices. Most lightweight cryptography focuses on using resources efficiently to operate in the resource-constrained devices. However, as a cryptography, it is still important to maintain security even from the potential attacks using not only conventional computers, but also the upcoming quantum computers.  
The advent of quantum computers and quantum algorithms has dramatically changed the cryptography community. The most well-known modern public key cryptography, such as RSA and Elliptic Curve Cryptography (ECC), are based on the difficulties of factorization and discrete algebra problem [3]. However, [PERSON]'s algorithm can perform prime number factorization efficiently, making RSA and ECC vulnerable [4].  
In the field of symmetric key cryptography, the impact of quantum computers is not as critical as the case of the public key cryptography. The Grover search algorithm can be used to find the \(n\)-bitsecret key at the speed of \(\sqrt{n}\), which is the most effective quantum attack method for block ciphers [5]. Applying the Grover search algorithm to block ciphers is the most efficient way to measure the security level of block ciphers against attacks from quantum computers. For this reason, not only the [PERSON]'s algorithm but also the cryptography must be implemented with a quantum circuit for cryptanalysis. Since the development of quantum computer is a rudimentary stage, finding the optimal quantum resource for the target algorithm is one of the most important research fields.  
In order to estimate the quantum resources, a number of block cipher implementations have been investigated [6; 7; 8; 9]. [PERSON] et al. estimated the quantum resource required for AES block cipher to apply the Grover search algorithm [6]. Afterward, [PERSON] et al. and [PERSON] et al. found more optimal substitute layer design in quantum circuits than [PERSON] et al. [7; 8]. Recently, [PERSON] et al. implemented the SIMON in quantum gates [9], which is a block cipher developed by the National Security Agency (NSA) to support the hardware environment [10].  
In this paper, we implemented SPECK and every Korean lightweight block cipher for the quantum resource estimation. To optimize the quantum circuit, functions, such as the key scheduling and the round functions, were optimized by simultaneously calculating results. In addition, the number of qubits was reduced by efficiently arranging the order of operations and the order of objects. Target ciphers are ARX-based structures designed with Addition, Rotation, and XOR operations.