登录   |   注册
    准考证打印   论文投票   报考指南   论文辅导   软考培训   郑重申明  
您现在的位置:  首页 > 软考学苑 > 软考历年真题 > 信息安全工程师-真题 >> 正文
正文
2019年信息安全工程师上午基础知识真题(八)
来源: 作者: 时间;2019-07-12 15:30:34 点击数: 尚大软考交流群:376154208
71-75、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
尚大教育,教育至尚,人才为大。

71-75、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)designs which have been designated cryptography standards by the US government (though DES's designation was finally withdrawn after the AES was adopted).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.collisons

B.image

C.preimage

D.solution

尚大教育,教育至尚,人才为大。
 
   各省软考办 
 
来顶一下
返回首页
返回首页
上一篇:2019年信息安全工程师上午基础知识真题(七)
下一篇:2019年信息安全工程师下午真题(一)
 相关文章
 
 
跟贴共
笔 名 :   验证码:
网友评论仅供其表达个人看法,并不表明尚大教育同意其观点或证实其描述
距离2022年05月28-29日软考考试还有
尚大软考交流群:376154208
软考各地考务机构
历年真题汇总




各省市软考报名简章