| 摘要: | 密碼系統的安全性取決於密鑰管理機制的完備與否，因此密鑰交換的設計對整個管理機制而言，是相當關鍵的環節。針對上述考量，我們提出量子密碼作為解決的思考方向。相較於現行的公開金鑰密碼系統，量子密碼所採取的方式雖然不同，但具有無條件安全的特性，因此量子密碼的應用前景廣為看好，是目前資訊安全與密碼學術上備受矚目的研究重點之一。電腦科技日新月異，一日千里，一旦量子電腦的發展進入實作階段，現行的密碼系統都將形同虛設，毫無安全性可言，然而量子密碼系統的無條件安全性，可以確保整個系統架構即使處於量子電腦的環境之下，也不至於有安全上的顧慮，因此該密碼系統的研發目前已是箭在弦上。從公開金鑰密碼系統提出以來，就有許多研究以種種數學難題為基礎，以安全性及效能為考量點，探討所有可能的解決方法，其中以基於大整數分解與離散對數問題的接受度較高，但在次指數演算法的部分，無論是大整數分解問題或離散對數問題，仍然存在很多的質疑；此外，上述兩種方法過於簡易的數學背景也存在相當的爭議。因此，發展更新更安全的機制作為密碼系統防護的安全保障，一直是相關研究領域致力完成的目標。量子密碼學正是以此目標為發展背景，運用物理規律探測系統是否遭到侵入竊聽。在量子力學中，測量不再是一種外部的、消極的過程，而是被測量系統內部的組成部分，一旦偵測到竊聽，必然會改變系統的狀態。換言之，除非系統設計者本身可以得知該系統的量子狀態，竊聽者無從也無能得知該系統內部的量子狀態，或複製一套相同的系統，因此，所有企圖侵入量子密碼系統進行竊聽的行為，都將無所遁形。本計畫以量子密碼學為研究重點，以相關的研究理論為安全性分析的根據，作為設計具備安全與效能的密碼系統的理論基礎，並且將所提出的量子密碼系統應用在相關研究上，提高系統的實作性。
The security of cryptosystem depends on the complete design toward a management scheme of secret keys. For the whole management scheme, the exchange of keys is a quite important part in designing the scheme. Aimed at the above-mentioned, quantum cryptography is directed to solve the information security problems. In comparison with the solutions of the current public-key cryptosystem, what is adopted by quantum cryptography is completely different. To the requirements of security, a quantum cryptosystem is provided with the characteristic of unconditional security so that its foreground is widely expected. Therefore, quantum cryptography nowadays has become one focus of the information security research. Computer technology changes and makes great progress with each passing day. Once the quantum computers are developed in practice, the current cryptosystems will exist in name only without secure functions. The characteristic of unconditional security is the best superiority to develop a quantum cryptosystem. Such a cryptosystem enables to construct a complete secure system even under the environment of quantum computer. Since the public-key cryptosystem is proposed, a considerable number of studies based on the varied kinds of mathematic problems have been made on the improvement of both security and efficiency. Only both large integers decomposition and discrete logarithm problems are widely accepted. In the part of sub-exponential algorithm; however, the above two problems are quite questioned. Besides, their over-simple mathematic background exists the secure subjects of controversy. Thus, the goal to develop a newer and securer cryptoscheme always guides the related researcher to achieve an unconditional-secure cryptosystem. Under such an expectation, quantum cryptography is developed to detect if there exists any wiretap using the change of physical regularity. In quantum mechanics, the measurement is no longer an external and passive process but an internal component of the measured system. Once any wiretap is detected, the statement of system will be changed. In other words, only the designer of the system himself enables to hear of the quantum statement of the system, no other enables to hear of the internal quantum statement. In the way, he who wiretaps disables to copy the same system. Therefore, all illegal attempts to invade a quantum cryptosystem cannot escape from being detected. Considering the integration of quantum mechanics and cryptography research into the practical application, the project is intended as an investigation of quantum cryptosystem to analyze its security. Besides, with the prerequisite of unconditional security, we devote ourselves to a cryptosystem with high efficiency so that the related research can be further put into effect. |
