【正文】 公鑰或者公鑰是可訪問的 .那么我們就可以進(jìn)行安全的通信 .這種通信可以抗竊聽 (見圖 ) 、篡改 (見圖 )。 4. A 放棄 PUa和 PRa， B 放棄 PUa。那 么他可用下列方式對 通信造成危害但又不被發(fā)現(xiàn) : 1. A 產(chǎn)生公 /私鑰對 [PUa,PRa]，并將含有 PUa和其標(biāo)識 IDA的消息發(fā)送給 B。 其有保密性和棄實(shí)性的密鑰分配 圖 中給出的方法建立在 [NEED78]中提出的一種方法之上，它既可抗主動攻擊又可 抗被動攻擊。 5. B 計(jì)算 DPRa[DPUa[M]]得到密鑰。因?yàn)楣€加密和解密計(jì)算量大，所以若用公鑰密碼進(jìn)行會話密鑰的交換。 4. A 選擇密鑰 KA，并將 M =EPRa[EPUa[KA]社氣〔戈 ]」發(fā)送給 B。 A 和 B 用 KA來交換消息； E不 再主動干擾通信信道而只需竊聽即可。 不過該協(xié)議容易受主動攻擊。 3． A 計(jì)算 DPRa[EPUa[KA]]得出秘密鑰 KA。因此，時(shí)間戳有些像截止日期。每一通信方向證書管理員提供一個(gè)公鑰并提出申請證書 請求。 證書包含公鑰和其他一些信息，它由證書管理員嚴(yán)生，井發(fā)給擁有相應(yīng)私鑰的通信方。 這樣 .總共需要發(fā)送七條消息。這樣 A 可以確定它收到的不是來自管理員的舊消息，該舊消息中包含的不是 B 的當(dāng)前公鑰。想前面一樣，該方案中假定中心管理員負(fù)責(zé)維護(hù)通信各方公鑰的動態(tài)目錄，除此之外，每一通信方可靠地知道該目錄管理員的公鑰，并且只有管理員知道相應(yīng)的私鑰。 2. 每一通信方通過目錄管理員來注冊一個(gè)公鑰。 ? a = e. (A5) Commutative: a ? b = b ? a for all a, b in G. A number of publickey ciphers are based on the use of an abelian group. For example, DiffieHellman key exchange involves multiplying pairs of nonzero integers modulo a prime number q. Keys are generated by exponentiation over the group, with exponentiation defined as repeated multiplication. For elliptic curve cryptography, an operation over elliptic curves, called addition, is used. Multiplication is defined by repeated addition. An elliptic curve is defined by an equation in two variables, with coefficients. For cryptography, the variables and coefficients are restricted to elements in a finite field, which results in the definition of a finite abelian group. Before looking at this, we first look at elliptic curves in which the variables and coefficients are real numbers. This case is perhaps easier to visualize. 外文資料翻譯 —— 譯文 密鑰管理 在第 7 章中，我們層討論了傳統(tǒng)密碼體制的密鑰分配問題。s CESG published the identical scheme a few months earlier in a classified document [WILL76] and claims to have discovered it several years prior to that。s private key is learned by an adversary. A generates a new private/public key pair and applies to the certificate authority for a new certificate. Meanwhile, the adversary replays the old certificate to B. If B then encrypts messages using the promised old public key, the adversary can read those messages. In this context, the promise of a private key is parable to the loss of a credit card. The owner cancels the credit card number but is at risk until all possible municants are aware that the old credit card is obsolete. Thus, the timestamp serves as something like an expiration date. If a certificate is sufficiently old, it is assumed to be expired. One scheme has bee universally accepted for formatting publickey certificates: the standard. certificates are used in most work security applications, including IP security, secure sockets layer (SSL), secure electronic transactions (SET), and S/MIME, all of which are discussed in Part Two. is examined in detail in Chapter 14. Distribution of Secret Keys Using PublicKey Cryptography Once public keys have been distributed or have bee accessible, secure munication that thwarts eavesdropping (Figure ), tampering (Figure ), or both (Figure ) is possible. However, few users will wish to make exclusive use of publickey encryption for munication because of the relatively slow data rates that can be achieved. Accordingly, publickey encryption provides for the distribution of secret keys to be used for conventional encryption. Simple Secret Key Distribution An extremely simple scheme was put forward by Merkle [MERK79], as illustrated in Figure . If A wishes to municate with B, the following procedure is employed: 1. A generates a public/private key pair {PUa, PRa} and transmits a message to B consisting of PUa and an identifier of A, IDA. 2. B generates a secret key, Ks, and transmits it to A, encrypted with A39。s nonce (N1) as well as a new nonce generated by B (N2) Because only B could have decrypted message (3), the presence of N1 in message (6) assures A that the correspondent is B. 6. A returns N2, encrypted using B39。 大學(xué) 畢業(yè)設(shè)計(jì) (論文 )外文資料翻譯 學(xué)院 (系 )： 計(jì)算機(jī)學(xué)院 專 業(yè)： 信息安全 學(xué)生姓名： 班級學(xué)號： 外文出處： William Stallings. Cryptography and Network Security, Fourth Edition. Prentice Hall. November 16, 2020 附件： ； 指導(dǎo)教師評語： 指導(dǎo)教師簽名： 年 月 日 外文資料翻譯 —— 原文 . Key Management In Chapter 7, we examined the problem of the distribution of secret keys. One of the major roles of publickey encryption has been to address the problem of key distribution. There are actually two distinct aspects to the use of publickey cryptography in this regard: ? The distribution of public keys ? The use of publickey encryption to distribute secret keys We examine each of these areas in turn. Distribution of Public Keys Several techniques have been proposed for the distribution of public keys. Virtually all these proposals can be grouped into the following general schemes: ? Public announcement ? Publicly available directory ? Publickey authority ? Publickey certificates Public Announcement of Public Keys On the face of it, the point of publickey encryption is that the public key is public. Thus, if there is some broadly accepted publickey algorithm, such as RSA, any participant can send his or her public key to any other participant or broadcast the key to the munity at large (Figure ). For example, because of the growing popularity of PGP (pretty good privacy, discussed in Chapter 15), which makes use of RSA, many PGP users have adopted the practice of appending their public key to messages that they send to public forums, such as USENET newsgroups and Inter mailing lists. Although this approach is convenient, it has a major weakness. Anyone can forge such a public announcement. That is, some user could pretend