gssecurity.java

java环境下编写的凯撒加密和解密算法

package gov.gwssi.xccore.util;
/**
 * 加密类
 */
import java.lang.Math;
public class GSSecurity {
    private static final int INT_RETURN_LOOP = 94;
     private static final int INT_PRIM_NUMBER = 95;
    /**
     * SysBean constructor comment.
     */
    public GSSecurity() {
        super();
    }
/**
 * 解密方法
 * @author tangzh
 * 创建日期 (2002-12-15 10:17:08)
 * @param strCode 需解密的字符串
 * @return 解密后的字符串
 * @version 1.0
 */
    public static String decode(String strCode) {
        String strOriginal;
        int intRnd;
        String strRnd;
        int intStrLen;

        String strDecodeMe = "";

        if (strCode.equals(""))
            return strDecodeMe;
        intStrLen = strCode.length() - 1;

        strRnd = strCode.substring(intStrLen / 2, intStrLen / 2 + 1);
        intRnd = strRnd.hashCode() - new GSSecurity().startChar();
        strCode =
            strCode.substring(0, intStrLen / 2)
                + strCode.substring(intStrLen / 2 + 1, intStrLen + 1);
        strOriginal =
            new GSSecurity().loopCode(strCode, INT_RETURN_LOOP - intRnd);
        strDecodeMe = strOriginal;
        return strDecodeMe;
    }
/**
 * 加密方法.随机取得加密的循环次数，使得每次加密所得的秘文会有所不同
 * @author tangzh
 * 创建日期 (2002-12-15 10:17:08)
 * @param strOriginal 需加密的字符串
 * @return 加密后的字符串
 * @version 1.0
 */
    public static String encode(String strOriginal) {
        String strCode;
        int intRnd;
        char rnd;
        int intStrLen;
        String strCodeMe = "";
        if (strOriginal.equals(""))
            return strCodeMe;
        //2 到 93 之间的随即数，即同一原文可能获得93种不同的秘文
        intRnd = (int) (Math.random() * (INT_RETURN_LOOP - 2) + 2);
        strCode = new GSSecurity().loopCode(strOriginal, intRnd);
        //对随机数作偏移加密
        rnd = (char) (intRnd + new GSSecurity().startChar());
        intStrLen = strCode.length();
        strCodeMe =
            strCode.substring(0, intStrLen / 2)
                + rnd
                + strCode.substring(intStrLen / 2, intStrLen);
        if(strCodeMe.indexOf("'")>= 0)
            return encode(strOriginal);
        else
            return strCodeMe;
    }
    //基础的凯撒算法,并对于每一位增加了偏移
    private String kaiserCode(String strOriginal) {
        int intChar;
        String strCode;
        int i;
        int intStrLen;
        int intTmp;

        intStrLen = strOriginal.length();

        strCode = "";
        for (i = 0; i < intStrLen; i++) {
            intChar = strOriginal.substring(i, i + 1).hashCode();
            intTmp = intChar - this.startChar();
            intTmp =
                (intTmp * INT_PRIM_NUMBER + i + 1) % this.maxChar()
                    + this.startChar();
            strCode = strCode + (char) (intTmp);
        }
        return strCode;
    }
    //循环调用凯撒算法一定次数后，可以取得原文
    private String loopCode(String strOriginal, int intLoopCount) {
        String strCode;
        int i;
        strCode = strOriginal;
        for (i = 0; i < intLoopCount; i++)
            strCode = this.kaiserCode(strCode);
        return strCode;
    }
public static void main(String[] args) {
    //加密
    String pw="admin";
    System.out.println(encode(pw));
    //解密
    System.out.println(decode("I4g%gT"));
}
    private int maxChar() {
        String str1 = "~";
        String str2 = "!";
        return str1.hashCode() - str2.hashCode() + 1;
    }
    private int startChar() {
        String str1 = "!";
        return str1.hashCode();
    }
}