【信息安全工程师201705】【4-8】

阅读下列说明，回答问题1至问题5，将解答写在答题纸的对应栏内。

【说明】

DES是一种分组密码，己知DES加密算法的某个S盒如表4-1所示。

真题详情及解析

【信息安全工程师201611】【70】在DES算法中，需要进行16轮加密，每一轮的子密钥长度为（70）位。

真题详情及解析

【信息安全工程师201611】【35】在DES加密算法中，密钥长度和被加密的分组长度分别是（35）。

真题详情及解析

【信息安全工程师201611】【26】已知DES算法S盒如下：

如果该S盒的输入110011，则其二进制输出为（26）。

真题详情及解析

【信息安全工程师201705】【4】（4）属于对称加密算法。

真题详情及解析

【信息安全工程师201805】【35】在DES加密算法中，子密钥的长度和加密分组的长度分别是（35）。

真题详情及解析

【信息安全工程师201805】【26】已知DES算法S盒如下：

如果该S盒的输入为100010，则其二进制输出为（26）。

真题详情及解析

【信息安全工程师201905】【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which have been designated cryptography standards by the US government （though DES's designation was finally withdrawn after the AES was adopted）.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.
yptographic 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.

真题详情及解析

【信息安全工程师201905】【48】安全电子交易协议SET中采用的公钥密码算法是RSA，采用的私钥密码算法是DES，其所使用的DES有效密钥长度是（48）。

真题详情及解析

【信息安全工程师201905】【26】已知DES算法S盒如下：

如果该S盒的输入110011，则其二进制输出为（26）。

真题详情及解析