凯撒密码加解密程序

【文件属性】：
文件名称：凯撒密码加解密程序
文件大小：5KB
文件格式：TXT
更新时间：2014-10-19 11:34:46
凯撒密码 凯撒密码加解密程序（C语言） 2009年09月30日 星期三 13:21 1、程序结构化，用函数分别实现 2、对文件的加密，解密输出到文件 #include #include void menu()/*菜单，1.加密 2.解密 3.退出*/ { clrscr(); printf("\n==============================================================================="); printf("\n1.Encrypt the file"); printf("\n2.Decrypt the file"); printf("\n3.Quit\n"); printf("===============================================================================\n"); printf("Please select a item:"); return; } char encrypt(char ch,int n)/*加密函数，把字符向右循环移位n*/ { while(ch>='A'&&ch<='Z') { return ('A'+(ch-'A'+n)%26); } while(ch>='a'&&ch<='z') { return ('a'+(ch-'a'+n)%26); } return ch; } main() { int i,n; char ch0,ch1; FILE *in,*out; char infile[10],outfile[10]; textbackground(RED); textcolor(LIGHTGREEN); clrscr(); menu(); ch0=getch(); while(ch0!='3') { if(ch0=='1') { clrscr(); printf("\nPlease input the infile:"); scanf("%s",infile);/*输入需要加密的文件名*/ 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);/*输入加密密码*/ printf("Please input the outfile:"); scanf("%s",outfile);/*输入加密后文件的文件名*/ 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))/*加密*/ { fputc(encrypt(fgetc(in),n),out); } printf("\nEncrypt is over!\n"); fclose(in); fclose(out); sleep(1); } if(ch0=='2') { clrscr(); printf("\nPlease input the infile:"); scanf("%s",infile);/*输入需要解密的文件名*/ 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);/*输入解密密码（可以为加密时候的密码）*/ n=26-n; printf("Please input the outfile:"); scanf("%s",outfile);/*输入解密后文件的文件名*/ 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(encrypt(fgetc(in),n),out); } printf("\nDecrypt is over!\n"); fclose(in); fclose(out); sleep(1); } clrscr(); printf("\nGood Bye!\n"); sleep(3); getch(); } }