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【信息安全工程师202011】【4-9】
阅读下列说明，回答问题1至问题6，将解答填入答题纸的对应栏内。
【说明】
ISO安全体系结构包含的安全服务有七大类，即：①认证服务；②访问控制服务；③数据保密性服务；④数据完整性服务；⑤抗否认性服务；⑥审计服务；⑦可用性服务。
请问以下各种安全威胁或者安全攻击可以采用对应的哪些安全服务来解决或者缓解。
请直接用上述编号①~⑦作答。

真题详情及解析

【信息安全工程师201905】【3-7】
阅读下列说明，回答问题1至问题5，将解答填入答题纸的对应栏内。
【说明】
假设用户A 和用户B为了互相验证对方的身份，设计了如下通信协议：
1.A->B：R_A
2.B->A：f（P_AB||R_A）||R_B
3.A->B：f（P_AB||）
其中： R_A、R_B是随机数， P_AB是双方事先约定并共享的口令，“||”表示连接操作。f是哈希函数。

真题详情及解析

【信息安全工程师201611】【4-7】
阅读下列说明，回答问题1至问题4，将解答填入答题纸的对应栏内。
【说明】
用户的身份认证是许多应用系统的第一道防线，身份识别对确保系统和数据的安全保密及其重要。以下过程给出了实现用户B对用户A身份的认证过程。
1、A->B：A
2、B->A：{B,Nb}pk(A)
3、A->B：h(Nb)
此处A和B是认证实体，Nb是一个随机值，pk(A)表示实体A的公钥，{B,Nb}pk(A)表示用A的公钥对消息B、Nb进行加密处理，h(Nb)表示用哈希算法h对Nb计算哈希值。

真题详情及解析

【信息安全工程师201611】【67】杂凑函数SHA1的输入分组长度为（67）比特。

真题详情及解析

【信息安全工程师201705】【35】SHA1算法的消息摘要长度是（35）位。

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【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which have been designated cryptography standards by the US government （though DES's designation was finally withdrawn after the AES was adopted）.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202111】【18】Hash算法是指产生哈希值或杂凑值的计算方法。MD5算法是由Rivest设计的Hash算法，该算法以512比特数据块为单位处理输入，产生（18）的哈希值。

真题详情及解析