第65題： 在下圖給出的加密過(guò)程中Mi,i=1,2,…,n表示明文分組，Ci,i=1,2,…,n表示密文分組，IV表示初始序列，K表示密鑰，E表示分組加密。該分組加密過(guò)程的工作模式是（  ）。

A.ECB
B.CTR
C.CFB
D.PCBC
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第66題： 目前網(wǎng)絡(luò)安全形勢(shì)日趨復(fù)雜，攻擊手段和攻擊工具層出不窮，攻擊工具日益先進(jìn), 攻擊者需要的技能日趨下降。以下關(guān)于網(wǎng)絡(luò)攻防的描述中，不正確的是（  ）。
A.嗅探器Sniffer工作的前提是網(wǎng)絡(luò)必須是共享以太網(wǎng)
B.加密技術(shù)可以有效抵御各類系統(tǒng)攻擊
C.APT的全稱是高級(jí)持續(xù)性威脅
D.同步包風(fēng)暴(SYN Flooding)的攻擊來(lái)源無(wú)法定位
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第67題： （  ）攻擊是指借助于客戶機(jī)/服務(wù)器技術(shù),將多個(gè)計(jì)算機(jī)聯(lián)合起來(lái)作為攻擊平臺(tái)，對(duì)一個(gè)或多個(gè)目標(biāo)發(fā)動(dòng)DoS攻擊，從而成倍地提高拒絕服務(wù)攻擊的威力。
A.緩沖區(qū)溢出
B.分布式拒絕服務(wù)
C.拒絕服務(wù)
D. 口令
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第69題： 移位密碼的加密對(duì)象為英文字母，移位密碼采用對(duì)明文消息的每一個(gè)英文字母向前推移固定Key位的方式實(shí)現(xiàn)加密。設(shè)key=3，則對(duì)應(yīng)明文MATH的密文為(  )。
A. OCVJ
B. QEXL
C. PDWK
D. RFYM
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第70題： 基于公開(kāi)密鑰的數(shù)字簽名算法對(duì)消息進(jìn)行簽名和驗(yàn)證時(shí)，正確的簽名和驗(yàn)證方式是（  ）。
A.發(fā)送方用自己的公開(kāi)密鑰簽名，接收方用發(fā)送方的公開(kāi)密鑰驗(yàn)證
B.發(fā)送方用自己的私有密鑰簽名，接收方用自己的私有密鑰驗(yàn)證
C.發(fā)送方用接收方的公開(kāi)密鑰簽名，接收方用自己的私有密鑰驗(yàn)證
D.發(fā)送方用自己的私有密鑰簽名，接收方用發(fā)送方的公開(kāi)密鑰驗(yàn)證
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第71題： The modern study of symmetric-key ciphers relates mainly to the study of block ciphers and stream ciphers and to their applications. A block cipher is, in a sense, a modern embodiment of Alberti's polyalphabetic cipher: block ciphers take as input a block of （71 ）and a key, and output a block of ciphertext of the same size. Since messages are almost always longer than a single block, some method of knitting together successive blocks is required. Several have been developed, some with better security in one aspect or another than others. They are the mode of operations and must be carefully considered when using a block cipher in a cryptosystem.
The Data Encryption Standard (DES) and the Advanced Encryption Standard (AES) are( 72 )designs which have been designated cryptography standards by the US government (though DES's designation was finally withdrawn after the AES was adopted). Despite its deprecation as an official standard, DES (especially its still-approved and much more secure triple-DES variant) remains quite popular; it is used across a wide range of applications, from ATM encryption to e-mail privacy and secure remote access. Many other block ciphers have been designed and released, with considerable variation in quality. Many have been thoroughly broken. See Category: Block ciphers.
Stream ciphers, in contrast to the ‘block’type, create an arbitrarily long stream of key material, which is combined ( 73 )the plaintext bit-by-bit or character-by-character, somewhat like the one-time pad. In a stream cipher, the output( 74 )is created based on an internal state which changes as the cipher operates. That state change is controlled by the key, and, in some stream ciphers, by the plaintext stream as well. RC4 is an example of a well-known, and widely used, stream cipher; see Category: Stream ciphers.
Cryptographic hash functions (often called message digest functions) do not necessarily use keys, but are a related and important class of cryptographic algorithms. They take input data (often an entire message), and output a short fixed length hash, and do so as a one-way function. For good ones, ( 75 ) (two plaintexts which produce the same hash) are extremely difficult to find.
Message authentication codes (MACs) are much like cryptographic hash functions, except that a secret key is used to authenticate the hash value on receipt. These block an attack against plain hash functions.
（71）
A.plaintext
B.ciphertext
C.data
D.hash
（72）
A.stream cipher
B.hash function
C.Message authentication code
D.Block cipher
（73）
A.of
B.for
C.with
D.in
（74）
A.hash
B.stream
C.ciphertext
D.plaintext
（75）
A.collisions
B.image
C.preimage
D.solution
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