信息安全实验-凯撒加密加法乘法变换.doc

【实验目的】 1. 简单加密方法的原理 2. 凯撒密码的原理及程序的编写【实验设备与环境】（1）计算机（2）TC【实验步骤(内容)】凯撒密码就是单表代替密码，它的每一个明文字符都由其右边第3个（模26）字符代替（A由D代替，B由E代替,W由Z代替,X由A代替，Y由B代替，Z由C代替）。（1）加法变换c (m + k) mod 26其中m是明文对应的数据，c是与明文对应的密文数据，k是加密用的参数，叫密钥。比如：data security对应数据序列4，1，20，1，19，5，3，21，18，9，20，25，当k=5时，得密文序列9，6，25，6，24，10，8，0，23，14，25，4。(2)乘同余码： 移位或等间隔抽取码，明密文之间没有一一对应关系。（容易产生多义性）。变换按照同余乘法进行：加密变换：C=Pk (mod 26)， 解密变换：P=Ck (mod 26) ，密钥：k源程序：#include#include char sumjiami(char ch,int n)n=n%10;while(ch=A&ch=a&ch=0&ch=A&ch=a&ch=0&ch=A&ch=a&ch=0&ch=A&ch=Z) for(i=0;i=0&h=a&ch=z) for(i=0;i=0&h=0&ch=9) for(i=0;i=0&h=9) return (0+h); return ch;void menu()printf(n=);printf(n1.sumjiami the file);printf(n2.muljiami the file);printf(n3.sumjiemi the file);printf(n4.muljiemi the file);printf(n5.Quitn);printf(=n);printf(Please select a item:);return;void main()int i,n;char ch0,ch1;FILE *in,*out;char infile20,outfile20;sleep(3);menu();ch0=getch();while(ch0!=5) if(ch0=1) clrscr(); printf(nPlease input the infile:); scanf(%s,infile); if(in=fopen(infile,r)=NULL) printf(Can not open the infile!n); printf(Press any key to exit!n); getch(); exit(0); printf(Please input the key:); scanf(%d,&n); printf(Please input the outfile:); scanf(%s,outfile); if(out=fopen(outfile,w)=NULL) printf(Can not open the outfile!n); printf(Press any key to exit!n); fclose(in); getch(); exit(0); while(!feof(in) fputc(sumjiami(fgetc(in),n),out); printf(nsumjiami is over!n); fclose(in); fclose(out); sleep(1); if(ch0=2) clrscr(); printf(nPlease input the infile:); scanf(%s,infile); if(in=fopen(infile,r)=NULL) printf(Can not open the infile!n); printf(Press any key to exit!n); getch(); exit(0); printf(Please input the key:); scanf(%d,&n); printf(Please input the outfile:); scanf(%s,outfile); if(out=fopen(outfile,w)=NULL) printf(Can not open the outfile!n); printf(Press any key to exit!n); fclose(in); getch(); exit(0); while(!feof(in) fputc(muljiami(fgetc(in),n),out); printf(nmuljiami is over!n); fclose(in); fclose(out); sleep(1); if(ch0=3) clrscr(); printf(nPlease input the infile:); scanf(%s,infile); if(in=fopen(infile,r)=NULL) printf(Can not open the infile!n); printf(Press any key to exit!n); getch(); exit(0); printf(Please input the key:); scanf(%d,&n); printf(Please input the outfile:); scanf(%s,outfile); if(out=fopen(outfile,w)=NULL) printf(Can not open the outfile!n); printf(Press any key to exit!n); fclose(in); getch(); exit(0); while(!feof(in) fputc(sumjiemi(fgetc(in),n),out); printf(nsumjiemi is over!n); fclose(in); fclose(out); sleep(1); if(ch0=4) clrscr(); printf(nPlease input the infile:); scanf(%s,infile); if(in=fopen(infile,r)=NULL) printf(Can not open the infile!n); printf(Press any key to exit!n); getch(); exit(0); printf(Please input the key:); scanf(%d,&n); printf(Please input the outfile:); scanf(%s,outfile); if(out=fopen(outfile,w)=NULL) printf(Can not open the outfile!n); printf(Press any key to exit!n); fclose(in); getch(); exit(0); while(!feof(in) fputc(muljiemi(fgetc(in),n),out); printf(nmuljiemi is over!n); fclose(in); fclose(out); sleep(1); menu(); ch0=getch();clrscr(); printf(nGood Bye!n);sleep(3);运行：在C盘建立1.txt和2.txt，在文本1中输入以下信息：大写：ABCDEFGHIJKLMNOPKRSTUVWXYZ;小写：abcdefghijklmnopkrstuvwxyz;数字：0123456789.1、 加法（sum）加密 选择1加密运行结果：大写：FGHIJKLMNOPQRSTUPWXYZABCDE;小写：fghijklmnopqrstupwxyzabcde;数字：5678901234.2、 加法（sum）解密 选择3加法解密 运行结果：大写：ABCDEFGHIJKLMNOPKRSTUVWXYZ;小写：abcdefghijklmnopkrstuvwxyz;数字：0123456789.3、 乘法（mul）加密选择2乘法加密