第65題： 在下圖給出的加密過程中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： 目前網絡安全形勢日趨復雜，攻擊手段和攻擊工具層出不窮，攻擊工具日益先進, 攻擊者需要的技能日趨下降。以下關于網絡攻防的描述中，不正確的是（  ）。
A.嗅探器Sniffer工作的前提是網絡必須是共享以太網
B.加密技術可以有效抵御各類系統(tǒng)攻擊
C.APT的全稱是高級持續(xù)性威脅
D.同步包風暴(SYN Flooding)的攻擊來源無法定位
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第67題： （  ）攻擊是指借助于客戶機/服務器技術,將多個計算機聯(lián)合起來作為攻擊平臺，對一個或多個目標發(fā)動DoS攻擊，從而成倍地提高拒絕服務攻擊的威力。
A.緩沖區(qū)溢出
B.分布式拒絕服務
C.拒絕服務
D. 口令
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第69題： 移位密碼的加密對象為英文字母，移位密碼采用對明文消息的每一個英文字母向前推移固定Key位的方式實現(xiàn)加密。設key=3，則對應明文MATH的密文為(  )。
A. OCVJ
B. QEXL
C. PDWK
D. RFYM
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第70題： 基于公開密鑰的數(shù)字簽名算法對消息進行簽名和驗證時，正確的簽名和驗證方式是（  ）。
A.發(fā)送方用自己的公開密鑰簽名，接收方用發(fā)送方的公開密鑰驗證
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證
C.發(fā)送方用接收方的公開密鑰簽名，接收方用自己的私有密鑰驗證
D.發(fā)送方用自己的私有密鑰簽名，接收方用發(fā)送方的公開密鑰驗證
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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)designs which have been designated cryptography standards by the US government (though DES's designation was finally withdrawn after the AES was adopted).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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