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Conference Paper
T-depth Reduction Method for Efficient SHA-256 Quantum Circuit Construction
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- Authors
- Jongheon Lee, Sokjoon Lee, You-Seok Lee, Dooho Choi
- Issue Date
- 2021-12
- Citation
- International Conference on Information Security and Cryptology (ICISC) 2021 (LNCS 13218), pp.368-391
- Publisher
- Springer
- Language
- English
- Type
- Conference Paper
- Abstract
- In order to perform a quantum brute force attack on a cryptosystem based on Grover's algorithm, it is necessary to implement a quantum circuit of the cryptographic algorithm. Therefore an efficient quantum circuit design of a given cryptographic algorithm is essential, especially in terms of quantum security analysis, and it is well known that T -depth should be reduced for time complexity efficiency.In this paper, we propose a novel technique to reduce T -depth (and T -count) when some quantum circuits located in between two T of f oligates are interchangeable with a controlled phase gate (Controlled-P gate), and apply this technique to four types of quantum adders, resulting in a T -depth reduction of about 33%.We also present new SHA-256 quantum circuits which have a critical path with only 3 quantum adders while the critical paths of quantum circuits in the previous works consist of 7 or 9 quantum adders, and also apply our technique to the proposed SHA-256 quantum circuits and the included quantum adders. Among the previous results, the T -depth of the circuit with the smallest W idth 801 was approximately 109,104. On the other hand, that of the proposed SHA-256 quantum circuit with the width 799 is 16,121, which is remarkably reduced by about 85%. Furthermore, the other proposed quantum circuit only requires 768 qubits which is the smallest W idth compared to the previous results to the best of our knowledge.
- KSP Keywords
- Brute-force attack, Critical path, Cryptographic Algorithms, Depth reduction, Grover's Algorithm, Novel technique, Phase gate, Quantum circuit, Reduction method, SHA-256, T-depth