信息安全加密实验程序及实验报告

import java.util.Scanner; public class Caesar { public void caesarcipher(){ int input; System.out.println("凯撒加密器"); System.out.println("1.加密 2.解密"); Scanner in=new Scanner(System.in); input=in.nextInt(); switch(input){ case 1: System.out.println("请输入要加密的字符串"); String str=in.next(); //System.out.println(str.charAt(1)); int key=3; String Encryption=""; for(int i=0;i<str.length();i++){ char ch=str.charAt(i); if(ch>='a'&&ch<='z'){ if(ch>='x'&&ch<='z'){ ch-=26; ch+=key; } else { ch+=key; } } else if(ch>='A'&&ch<='Z'){ if(ch>='A'&&ch<='Z'){ ch-=26; ch+=key; } else { ch+=key; } } Encryption+=ch; } System.out.print("加密后的字符串为："); System.out.println(Encryption); break; case 2: System.out.println("请输入要解密的字符串："); String str1=in.next(); String Decrypt=""; for(int i=0;i<str1.length();i++){ char ch=str1.charAt(i); if(ch>='a'&&ch<='z'){ if(ch>='a'&&ch<='c'){ ch+=26; ch-=key; } else { ch-=key; } } else if(ch>='A'&&ch<='Z'){ if(ch>='A'&&ch<='Z'){ ch+=26; ch-=key; } else { ch+=key; } } Decrypt+=ch; } System.out.println("解密后的字符串为："+Decrypt); break; } } } public static void main(String[] args){ Caesar ca=new Caesar(); ca.caesarcipher(); } }