www.pudn.com > EncryDeCry.rar > EncryDeCry.java

我在字符串加密时的处理是每次取字符串的三个字节，再把三个字符连成一个24位的整型，前8位存放第一个字符，中间8位存放第二个字符，最后8位存放第三个字符。再取这个整型数的前6位对应的数值去差用户提供对应表，转化成相应的字符，再取第二个6位，第三个6位，第四个六位进行字符的转换。再重复前面相同的操作值到整个字符串转换完毕。在解密的过程就是根据用户提供的表进行查找和移位换原字符串。 
这种算法比通常的直接根据用户提供的表进行转换有更高的安全性，且加密解密的效率很高。 
具体的代码如下： 
          private static byte[] cvtTable = { 
        (byte)'A', (byte)'B', (byte)'C', (byte)'D', (byte)'E', 
        (byte)'F', (byte)'G', (byte)'H', (byte)'I', (byte)'J', 
        (byte)'K', (byte)'L', (byte)'M', (byte)'N', (byte)'O', 
        (byte)'P', (byte)'Q', (byte)'R', (byte)'S', (byte)'T', 
        (byte)'U', (byte)'V', (byte)'W', (byte)'X', (byte)'Y', 
        (byte)'Z', 
        (byte)'a', (byte)'b', (byte)'c', (byte)'d', (byte)'e', 
        (byte)'f', (byte)'g', (byte)'h', (byte)'i', (byte)'j', 
        (byte)'k', (byte)'l', (byte)'m', (byte)'n', (byte)'o', 
        (byte)'p', (byte)'q', (byte)'r', (byte)'s', (byte)'t', 
        (byte)'u', (byte)'v', (byte)'w', (byte)'x', (byte)'y', 
        (byte)'z', 
        (byte)'0', (byte)'1', (byte)'2', (byte)'3', (byte)'4', 
        (byte)'5', (byte)'6', (byte)'7', (byte)'8', (byte)'9', 
        (byte)'/', (byte)';' 
    }; 
    static String encode(String content) { 
        byte input[] = (content).getBytes(); 
        byte[] output; 
        //System.out.println("input[] length = "+input.length); 
        if(input.length%3 == 0) { 
            //System.out.println("xxxxx"); 
            output = new byte[input.length/3*4]; 
        } 
        else  
            output = new byte[((input.length / 3) + 1) * 4]; 
        int ridx = 0; 
        int chunk = 0; 
 
        for (int i = 0; i < input.length; i += 3) { 
            int left = input.length - i; 
            if (left > 2) { 
                chunk = (input[i] << 16)| 
                        (input[i + 1] << 8) | 
                         input[i + 2]; 
                output[ridx++] = cvtTable[(chunk&0xFC0000)>>18]; 
                output[ridx++] = cvtTable[(chunk&0x3F000) >>12]; 
                output[ridx++] = cvtTable[(chunk&0xFC0)   >> 6]; 
                output[ridx++] = cvtTable[(chunk&0x3F)]; 
            } else if (left == 2) { 
                chunk = (input[i] << 16) | 
                        (input[i + 1] << 8); 
                output[ridx++] = cvtTable[(chunk&0xFC0000)>>18]; 
                output[ridx++] = cvtTable[(chunk&0x3F000) >>12]; 
                output[ridx++] = cvtTable[(chunk&0xFC0)   >> 6]; 
                output[ridx++] = cvtTable[63]; 
            } else if(left == 1){ 
                chunk = input[i] << 16; 
                output[ridx++] = cvtTable[(chunk&0xFC0000)>>18]; 
                output[ridx++] = cvtTable[(chunk&0x3F000) >>12]; 
                output[ridx++] = cvtTable[63]; 
                output[ridx++] = cvtTable[63]; 
            } 
        } 
        return new String(output); 
    } 
          static String revert(String content) { 
        byte tempArray[] = (content).getBytes(); 
        byte[] result = new byte[tempArray.length/4*3]; 
        int temp = 0; 
        int pos = 0; 
 
        //for(int i= tempArray.length-1;i>= 0;i--) 
           //System.out.println(tempArray[i]); 
         
        for(int i = 0;i < tempArray.length;i += 4) { 
 
            temp = (search(tempArray[i]) << 18) |  
                   (search(tempArray[i+1]) << 12) | 
                   (search(tempArray[i+2]) << 6) | 
                   (search(tempArray[i+3])); 
             
            result[pos++] = (byte)((temp & 0xff0000) >> 16); 
            result[pos++] = (byte)((temp & 0xff00) >> 8); 
            result[pos++] = (byte)(temp & 0xff); 
        } 
        return new String(result); 
    } 
    static int search(int target) { 
        int  i = 0; 
        while(target != cvtTable[i] && i < 64) { 
            i++; 
        } 
        return i; 
    }