Java/IOS通用异或加解密字符串

05 May 2014

Reading time ~2 minutes

Java的异或加解密算法

在使用异或加解密时，加密和解密的密钥必须保持相同，否则解密时无法恢复为原来的内容。

public class XOREncryptAndDecrypt {

	//密钥 加解密的密钥必须相同 可自定义
	private static final String secretKey ="abcdefghijklmnopqrstuvwxyz";

	/**
	 * 字符串加密
	 * @param plainText 要加密的字符串
	 * @return 加密后的字符串
	 */
	public static String encrypt(String plainText){
		 String encryption = "";
		 try {
			 plainText =  new String(plainText.getBytes("UTF-8"),"iso-8859-1");
			} catch (Exception e) {
			}
	     char[] cipher=new char[plainText.length()];
	     for(int i=0,j=0;i<plainText.length();i++,j++){
	         if(j==secretKey.length())
	             j=0;
	         cipher[i]=(char) (plainText.charAt(i)^secretKey.charAt(j));
	         String strCipher= Integer.toHexString(cipher[i]);
	         if(strCipher.length() == 1){
	        	 encryption+="0"+strCipher;
	         }else{
	        	 encryption+=strCipher;
	         }
	     }
	     return encryption;
	 }

	/**
	 * 解密字符串
	 * @param encryption 要解密的字符串
	 * @return 解密后的字符串
	 */
	public static String decrypt(String encryption) {
	     char[] decryption=new char[encryption.length()/2];
	     for(int i=0,j=0;i<encryption.length()/2;i++,j++){
	         if(j==secretKey.length())
	             j=0;
	         char n=(char)(int)Integer.valueOf(encryption.substring(i*2,i*2+2),16);
	         decryption[i]=(char)(n^secretKey.charAt(j));
	     }
	     String decoding="";
	     try {
	    	 decoding = new String(String.valueOf(decryption).getBytes("iso-8859-1"),"UTF-8");
		 		} catch (Exception e) {
			}
	     return decoding;
	 }

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		String name="你好";
		 String tem=XOREncryptAndDecrypt.encrypt(name);
		 System.out.println(tem);
		 System.out.println(XOREncryptAndDecrypt.decrypt(tem));

	}

}

iOS加解密算法

在使用异或加解密时，加密和解密的密钥必须保持相同，否则解密时无法恢复为原来的内容。如果想在IOS与Java中通用，必须保持Java与IOS中的密钥一致。

.h文件内容

#import <Foundation/Foundation.h>

@interface XOREncryptAndDecrypt : NSObject

/**
 *  字符串加密
 *
 *  @param plainText 要加密的字符串
 *
 *  @return 加密后的字符串
 */
+ (NSString *)encryptForPlainText:(NSString *)plainText;

/**
 *  解密字符串
 *
 *  @param encryption 要解密的字符串
 *
 *  @return 要解密的字符串 如果不为加密字符则返回原字符串
 */
+ (NSString *)decryptForEncryption:(NSString *)encryption;

@end

.m文件内容

#import "XOREncryptAndDecrypt.h"

@implementation XOREncryptAndDecrypt

static NSString *secretKey =@"abcdefghijklmnopqrstuvwxyz"; ///<密钥 加解密的密钥必须相同 可自定义

#pragma mark 加密字符串

+ (NSString *)encryptForPlainText:(NSString *)plainText
{
    //保存加密后的字符
    NSMutableString *encryption=[NSMutableString string];
    //编码转换后的字符串 UTF_8->iso-8859-1
    NSString *encoding=[[NSString alloc]initWithData:[plainText dataUsingEncoding:NSUTF8StringEncoding] encoding:NSISOLatin1StringEncoding];

    for(int i=0,j=0;i<encoding.length;i++,j++){
        if(j==secretKey.length){
            j=0;
        }
        //异或后的字符
        char cipher=(char)([encoding characterAtIndex:i]^[secretKey characterAtIndex:j]);
        //NSLog(@"%c转成16进制的字符串：%@,%@",cipher,[NSString stringWithFormat:@"%hhx",cipher],[NSString stringWithFormat:@"%x",cipher&0xff]);
        //转成16进制形式的字符串 \x8b转成8b字符串
        NSString *strCipher= [NSString stringWithFormat:@"%hhx",cipher];
        if(strCipher.length == 1){
            [encryption appendFormat:@"0%@",strCipher];
        }else{
            [encryption appendString:strCipher];
        }
    }
    return encryption;
}

#pragma mark 解密 如果不为加密字符则返回原字符

+ (NSString *)decryptForEncryption:(NSString *)encryption {
    //保存解密后的字符
    NSMutableString *decryption=[NSMutableString string];
    //解码字符
    NSString *decoding=nil;

    for(int i=0,j=0;i<encryption.length/2;i++,j++){
        if(j==secretKey.length){
            j=0;
        }
        //截取16进制形式的字符串 \x8b中的8b
        NSString *tem=[encryption substringWithRange:NSMakeRange(i*2, 2)];
        char *endptr;
        //把16进制形式的字符串转为字符
        char n=(char)(int)strtoul([tem UTF8String],&endptr,16);
        //判断是否为加密字符
        if (n=='\0'&&*endptr!='\0') {
            [decryption setString:@""];
            break;
        }
        [decryption appendFormat:@"%c",(char)(n^[secretKey characterAtIndex:j])];
    }
    if (![decryption isEqualToString:@""]) {
        //编码后的字符串 iso-8859-1 -> UTF_8
        decoding=[[NSString alloc]initWithData:[[decryption copy] dataUsingEncoding:NSISOLatin1StringEncoding] encoding:NSUTF8StringEncoding];
    }
    if (decoding==nil) {
        decoding=encryption;
    }
    return decoding;
}

@end