主要是要得到加密后的原来的字符创，MD5无法得到原有的，只能用AES+base64

要用GTMBase64这个可以自己去下载，

主要看另外2个类文件，

#import <Foundation/Foundation.h>
@class NSString;
@interface NSData (NSData_AES)

- (NSData *)AES128EncryptWithKey:(NSString *)key;   //加密
- (NSData *)AES128DecryptWithKey:(NSString *)key;   //解密

@end

#import "NSData+NSData_AES.h"
#import <CommonCrypto/CommonCryptor.h>
#define gIv @"xxxxxxxxxxx" //可以自行定义16位

@implementation NSData (NSData_AES)
//(key和iv向量这里是16位的) 这里是CBC加密模式，安全性更高

- (NSData *)AES128EncryptWithKey:(NSString *)key//加密
{
    char keyPtr[kCCKeySizeAES128+1];
    bzero(keyPtr, sizeof(keyPtr));
    [key getCString:keyPtr maxLength:sizeof(keyPtr) encoding:NSUTF8StringEncoding];
    
    char ivPtr[kCCKeySizeAES128+1];
    memset(ivPtr, 0, sizeof(ivPtr));
    [gIv getCString:ivPtr maxLength:sizeof(ivPtr) encoding:NSUTF8StringEncoding];
    
    NSUInteger dataLength = [self length];
    size_t bufferSize = dataLength + kCCBlockSizeAES128;
    void *buffer = malloc(bufferSize);
    size_t numBytesEncrypted = 0;
    CCCryptorStatus cryptStatus = CCCrypt(kCCEncrypt,
                                          kCCAlgorithmAES128,
                                          kCCOptionPKCS7Padding,
                                          keyPtr,
                                          kCCBlockSizeAES128,
                                          ivPtr,
                                          [self bytes],
                                          dataLength,
                                          buffer,
                                          bufferSize,
                                          &numBytesEncrypted);
    if (cryptStatus == kCCSuccess) {
        return [NSData dataWithBytesNoCopy:buffer length:numBytesEncrypted];
    }
    free(buffer);
    return nil;
}


- (NSData *)AES128DecryptWithKey:(NSString *)key//解密
{
    char keyPtr[kCCKeySizeAES128+1];
    bzero(keyPtr, sizeof(keyPtr));
    [key getCString:keyPtr maxLength:sizeof(keyPtr) encoding:NSUTF8StringEncoding];
    
    char ivPtr[kCCKeySizeAES128+1];
    memset(ivPtr, 0, sizeof(ivPtr));
    [gIv getCString:ivPtr maxLength:sizeof(ivPtr) encoding:NSUTF8StringEncoding];
    
    NSUInteger dataLength = [self length];
    size_t bufferSize = dataLength + kCCBlockSizeAES128;
    void *buffer = malloc(bufferSize);
    size_t numBytesDecrypted = 0;
    CCCryptorStatus cryptStatus = CCCrypt(kCCDecrypt,
                                          kCCAlgorithmAES128,
                                          kCCOptionPKCS7Padding,
                                          keyPtr,
                                          kCCBlockSizeAES128,
                                          ivPtr,
                                          [self bytes],
                                          dataLength,
                                          buffer,
                                          bufferSize,
                                          &numBytesDecrypted);
    if (cryptStatus == kCCSuccess) {
        return [NSData dataWithBytesNoCopy:buffer length:numBytesDecrypted];
    }
    free(buffer);
    return nil;
}

@end

#import <Foundation/Foundation.h>

@interface SecurityUtil : NSObject 

#pragma mark - base64
+ (NSString*)encodeBase64String:(NSString *)input;
+ (NSString*)decodeBase64String:(NSString *)input;

+ (NSString*)encodeBase64Data:(NSData *)data;
+ (NSString*)decodeBase64Data:(NSData *)data;

#pragma mark - AES加密
//将string转成带密码的data
+ (NSString*)encryptAESData:(NSString*)string app_key:(NSString*)key ;
//将带密码的data转成string
+(NSString*)decryptAESData:(NSData*)data app_key:(NSString*)key ;


@end

#import "SecurityUtil.h"
#import "GTMBase64.h"
#import "NSData+AES.h"


@implementation SecurityUtil

#pragma mark - base64
+ (NSString*)encodeBase64String:(NSString * )input { 
    NSData *data = [input dataUsingEncoding:NSUTF8StringEncoding allowLossyConversion:YES]; 
    data = [GTMBase64 encodeData:data]; 
    NSString *base64String = [[[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding] autorelease]; 
	return base64String;
}

+ (NSString*)decodeBase64String:(NSString * )input { 
    NSData *data = [input dataUsingEncoding:NSUTF8StringEncoding allowLossyConversion:YES]; 
    data = [GTMBase64 decodeData:data]; 
    NSString *base64String = [[[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding] autorelease]; 
	return base64String;
} 

+ (NSString*)encodeBase64Data:(NSData *)data {
	data = [GTMBase64 encodeData:data]; 
    NSString *base64String = [[[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding] autorelease];
	return base64String;
}

+ (NSString*)decodeBase64Data:(NSData *)data {
	data = [GTMBase64 decodeData:data]; 
    NSString *base64String = [[[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding] autorelease];
	return base64String;
}

#pragma mark - AES加密
//将string转成带密码的data
+(NSString*)encryptAESData:(NSString*)string app_key:(NSString*)key
{
    //将nsstring转化为nsdata
    NSData *data = [string dataUsingEncoding:NSUTF8StringEncoding];
    //使用密码对nsdata进行加密
    NSData *encryptedData = [data AES128EncryptWithKey:key];
    NSLog(@"加密后的字符串 :%@",[encryptedData base64Encoding]);
    
    return [encryptedData base64Encoding];
}

#pragma mark - AES解密
//将带密码的data转成string
+(NSString*)decryptAESData:(NSData*)data  app_key:(NSString*)key
{
    //使用密码对data进行解密
    NSData *decryData = [data AES128DecryptWithKey:key];
    //将解了密码的nsdata转化为nsstring
    NSString *str = [[NSString alloc] initWithData:decryData encoding:NSUTF8StringEncoding];
    NSLog(@"解密后的字符串 :%@",str);
    return [str autorelease];
}

@end

加密：

[SecurityUtilencryptAESData:@"XXXXXX" app_key:KEY]; 这里的是可以自己设置一个16位的字符串

解密：

NSData *EncryptData1 = [GTMBase64decodeString:[SecurityUtil encryptAESData:@"XXXXXX" app_key:KEY]];//解密前进行GTMBase64编码

NSString * string1 = [SecurityUtildecryptAESData:EncryptData1app_key:KEY];

iOS AES的加密解密