本文選題：Mix-Net　切入點：ElGamal　出處：《西安電子科技大學(xué)》2014年碩士論文

【摘要】：隨著Internet應(yīng)用的發(fā)展,特別是電子投票、網(wǎng)絡(luò)銀行和電子商務(wù)等應(yīng)用領(lǐng)域的日益廣泛,網(wǎng)絡(luò)通信不再局限于實現(xiàn)傳統(tǒng)密碼學(xué)所考慮的數(shù)據(jù)完整性、認(rèn)證性、秘密性和不可否認(rèn)性等安全特性,而越來越重視對通信實體隱私性的保護(hù)。匿名通信技術(shù)正是保護(hù)Internet用戶隱私的一種有效手段,它是一個極具活力的研究領(lǐng)域。其中,最具代表性的包括Chaum提出的Mix-Net和DC-Net,它們已被應(yīng)用到很多匿名通信系統(tǒng)中。然而,這些匿名通信系統(tǒng)雖然給用戶提供了匿名服務(wù),但是絕大多數(shù)都不支持多級匿名度。對于普通的匿名通信系統(tǒng)而言,匿名服務(wù)級別過高則導(dǎo)致消息延遲過大,而匿名服務(wù)級別過低則導(dǎo)致不安全性。顯然,兩種情況都會降低系統(tǒng)的服務(wù)質(zhì)量。即便是目前已有的支持多級匿名度的方案,也都存在結(jié)構(gòu)復(fù)雜、不易分析等缺點。針對以上問題,本文研究如何利用Mix-Net協(xié)議,構(gòu)造更實用的匿名通信系統(tǒng),使用戶能夠權(quán)衡消息匿名級別和轉(zhuǎn)發(fā)延遲,靈活選取合適的匿名級別和延遲參數(shù),并為此設(shè)計出兩種具體解決方案,這兩種方案均以ElGamal算法為基礎(chǔ),進(jìn)而確保消息安全性,同時對匿名消息進(jìn)行混洗使第三方無法通過流量分析確定通信雙方的對應(yīng)關(guān)系,進(jìn)而確保消息匿名性。其中,方案一采用單Mix服務(wù)器的結(jié)構(gòu),而方案二采用多個Mix服務(wù)器串聯(lián)的結(jié)構(gòu)。相比之下,方案二更加安全可靠,且通用性強,因為方案一主要存在單點失效的問題。本文著重介紹方案二,該系統(tǒng)本質(zhì)上充當(dāng)一個信任代理,能產(chǎn)生所有匿名級別對應(yīng)的加解密參數(shù)。客戶端根據(jù)不同的匿名級別,先向系統(tǒng)查詢相應(yīng)級別下的公鑰,再用ElGamal算法生成密文并發(fā)送到系統(tǒng)的輸入隊列。客戶端發(fā)送數(shù)據(jù)包的目的地址是信任代理的地址,而實際接收者的地址被隱藏在密文中。然后該代理每次都從輸入隊列中取出一個批次的消息,將這它們處理成明文消息(包括若干次的部分解密、混洗和再加密操作),并從明文中提取出實際目標(biāo)地址,按照目的地址轉(zhuǎn)發(fā)給相應(yīng)接收者。接收者所接收的數(shù)據(jù)包中,源路由地址已經(jīng)被替換為信任代理的地址,而實際發(fā)送者的地址被隱藏�？梢钥闯�,該方案中的數(shù)據(jù)包的實際源地址和實際目標(biāo)地址以加密方式隱藏后,只有代理的入口服務(wù)器能看到真正源地址,代理的出口服務(wù)器能看到真正目標(biāo)地址,而其它任何中間服務(wù)器都無法將實際源地址和目標(biāo)地址對應(yīng)起來。通過理論分析和實際測試,正式地證明了系統(tǒng)的安全性和匿名性,比前人的方案更有效。該方案能提供多級匿名通信服務(wù),而且可靠實用,能應(yīng)用到電子匿名郵件、電子競拍等多個領(lǐng)域中。
[Abstract]:With the development of Internet applications, especially in the fields of electronic voting, network banking and electronic commerce, network communication is no longer limited to the realization of data integrity and authentication, which are considered in traditional cryptography. Security features such as confidentiality and non-repudiation are paid more and more attention to the protection of privacy of communication entities. Anonymous communication technology is an effective means to protect the privacy of Internet users, and it is a very active research field. The most representative ones include Mix-Net and DC-Net. proposed by Chaum, which have been applied to many anonymous communication systems. However, although these anonymous communication systems provide anonymous services to users, However, most do not support multilevel anonymity. For common anonymous communication systems, too high an anonymous service level leads to excessive message latency, and too low an anonymous service level leads to insecurity. Both of them will reduce the quality of service of the system. Even the existing schemes that support multilevel anonymity also have some disadvantages, such as complex structure and difficult to analyze. In view of the above problems, this paper studies how to use Mix-Net protocol. A more practical anonymous communication system is constructed, which enables users to balance message anonymous level and forwarding delay, flexibly select appropriate anonymous level and delay parameters, and design two concrete solutions for this purpose. These two schemes are based on the ElGamal algorithm to ensure the security of the message. At the same time, the anonymous messages are mashed so that the third party can not determine the correspondence between the two parties through traffic analysis, and then ensure the anonymity of the message. The first scheme adopts the structure of single Mix server, while the second scheme adopts the structure of multiple Mix servers in series. In contrast, scheme two is more secure and reliable, and has strong versatility. This paper focuses on scenario two, which essentially acts as a trust agent, which can generate encryption and decryption parameters corresponding to all anonymous levels. First, the public key at the corresponding level is queried to the system, then the ciphertext is generated by ElGamal algorithm and sent to the input queue of the system. The destination address of the data packet sent by the client is the address of the trust agent. The addresses of the actual recipients are then hidden in the ciphertext. The agent then takes one batch of messages from the input queue at a time, processing them as plaintext messages (including several times of partial decryption), Shuffling and reencrypting operations, and extracting the actual destination address from the plaintext, forwarding it to the corresponding receiver according to the destination address. In the packet received by the receiver, the source routing address has been replaced with the address of the trust agent. But the address of the actual sender is hidden. It can be seen that only the proxy portal server can see the real source address after the actual source address and the actual destination address of the packet in the scheme are encrypted. The proxy's exit server can see the real target address, while no other intermediate server can match the actual source address to the target address. Through theoretical analysis and practical testing, the security and anonymity of the system are formally proved. This scheme can provide multilevel anonymous communication service, and it is reliable and practical, and can be used in many fields, such as email, electronic auction and so on.
【學(xué)位授予單位】：西安電子科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：TP393.08

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