在下图给出的加密过程中，Mi,i=1,2,…,n表示明文分组，Ci,i=1,2,…,n表示密文分组，IV表示初始序列，K表示密钥，E表示分组加密。该分组加密过程的工作模式是（ ）。
- A.EC
- B.CTR
- C.CFB
- D.PCBC
正确答案及解析
正确答案
解析
＜span微软雅黑",sans-serif;mso-bidi-font-family:宋体;color:windowtext;mso-ansi-language:en-us;mso-fareast-language:=""zh-cn;mso-bidi-language:ar-sa'=""style="box-sizing:border-box;-webkit-user-drag:auto!important;user-select:text!important;">本题考查分组密码相关知识。
＜span微软雅黑",sans-serif;mso-bidi-font-family:宋体;color:windowtext;mso-ansi-language:en-us;mso-fareast-language:=""zh-cn;mso-bidi-language:ar-sa'=""style="box-sizing:border-box;-webkit-user-drag:auto!important;user-select:text!important;">图为明密文链接工作原理图，即PCBC。官方教材（第一版）P109。
电码本模式ECB直接利用分组密码对明文的各分组进行加密。
＜span微软雅黑",sans-serif;mso-bidi-font-family:宋体;color:windowtext;mso-ansi-language:en-us;mso-fareast-language:=""zh-cn;mso-bidi-language:ar-sa'=""style="box-sizing:border-box;-webkit-user-drag:auto!important;user-select:text!important;">
计数模式（CTR模式）加密是对一系列输入数据块(称为计数)进行加密，产生一系列的输出块，输出块与明文异或得到密文。
密文反馈模式（CFB模式）。在CFB模式中，前一个密文分组会被送回到密码算法的输入端。
＜span微软雅黑",sans-serif;mso-bidi-font-family:宋体;color:windowtext;mso-ansi-language:en-us;mso-fareast-language:=""zh-cn;mso-bidi-language:ar-sa'=""style="box-sizing:border-box;-webkit-user-drag:auto!important;user-select:text!important;">故本题选D。
＜span微软雅黑",sans-serif;mso-bidi-font-family:宋体;color:windowtext;mso-ansi-language:en-us;mso-fareast-language:=""zh-cn;mso-bidi-language:ar-sa'=""style="box-sizing:border-box;-webkit-user-drag:auto!important;user-select:text!important;">明密文链接方式具有加密错误传播无界的特性，而磁盘文件加密通常希望解密错误传播有界，这时可采用密文链接方式。
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