iOS开发之AES+Base64数据混合加密与解密

作者: Bison | 来源:发表于2016-03-31 09:35 被阅读4463次

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"APP的数据安全已经牵动着我们开发者的心，简单的MD5/Base64等已经难以满足当下的数据安全标准，本文简单的介绍下AES与Base64的混合加密与解密"

AES:高级加密标准（英语：Advanced Encryption Standard，缩写：AES），在密码学中又称Rijndael加密法，是美国联邦政府采用的一种区块加密标准。这个标准用来替代原先的DES，已经被多方分析且广为全世界所使用。经过五年的甄选流程，高级加密标准由美国国家标准与技术研究院（NIST）于2001年11月26日发布于FIPS PUB 197，并在2002年5月26日成为有效的标准。2006年，高级加密标准已然成为对称密钥加密中最流行的算法之一。

以上是来自百度百科的解释。

下面我将用代码来阐述其使用方法。
首先我们创建一个NSData的类扩展，命名为AES，创建完如果对的话应该是这样的NSData+AES然后导入如下头文件

#import <CommonCrypto/CommonDigest.h>
#import <CommonCrypto/CommonCryptor.h>

再增加加解密的方法，方便外部文件的调用，写完.h文件如下

#import <Foundation/Foundation.h>
#import <CommonCrypto/CommonDigest.h>
#import <CommonCrypto/CommonCryptor.h>

@interface NSData (AES)

//加密
- (NSData *) AES256_Encrypt:(NSString *)key;

//解密
- (NSData *) AES256_Decrypt:(NSString *)key;

//追加64编码
- (NSString *)newStringInBase64FromData;

//同上64编码
+ (NSString*)base64encode:(NSString*)str;


@end

.m文件中依次实现这几个方法，具体如下

#import "NSData+AES.h"

static char base64[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

@implementation NSData (AES)

//加密
- (NSData *) AES256_Encrypt:(NSString *)key{
    char keyPtr[kCCKeySizeAES256+1];
    bzero(keyPtr, sizeof(keyPtr));
    [key getCString:keyPtr maxLength:sizeof(keyPtr) 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 | kCCOptionECBMode,
    keyPtr, kCCBlockSizeAES128,
    NULL,
    [self bytes], dataLength,
    buffer, bufferSize,
    &numBytesEncrypted);
    if (cryptStatus == kCCSuccess) {
        return [NSData dataWithBytesNoCopy:buffer length:numBytesEncrypted];
    }
    free(buffer);
    return nil;
}

//解密
- (NSData *) AES256_Decrypt:(NSString *)key{

    char keyPtr[kCCKeySizeAES256+1];
    bzero(keyPtr, sizeof(keyPtr));
    [key getCString:keyPtr maxLength:sizeof(keyPtr) 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 | kCCOptionECBMode,
    keyPtr, kCCBlockSizeAES128,
    NULL,
    [self bytes], dataLength,
    buffer, bufferSize,
    &numBytesDecrypted);
    if (cryptStatus == kCCSuccess) {
        return [NSData dataWithBytesNoCopy:buffer length:numBytesDecrypted];

    }
    free(buffer);
    return nil;
}

//追加64编码
- (NSString *)newStringInBase64FromData            

{

    NSMutableString *dest = [[NSMutableString alloc] initWithString:@""];

    unsigned char * working = (unsigned char *)[self bytes];

    int srcLen = (int)[self length];

    for (int i=0; i<srcLen; i += 3) {

        for (int nib=0; nib<4; nib++) {

            int byt = (nib == 0)?0:nib-1;

            int ix = (nib+1)*2;

            if (i+byt >= srcLen) break;

            unsigned char curr = ((working[i+byt] << (8-ix)) & 0x3F);

            if (i+nib < srcLen) curr |= ((working[i+nib] >> ix) & 0x3F);

            [dest appendFormat:@"%c", base64[curr]];

        }

    }

    return dest;

}



+ (NSString*)base64encode:(NSString*)str

{

    if ([str length] == 0)

    return @"";

    const char *source = [str UTF8String];

    int strlength  = (int)strlen(source);

    char *characters = malloc(((strlength + 2) / 3) * 4);

    if (characters == NULL)

    return nil;

    NSUInteger length = 0;

    NSUInteger i = 0;

    while (i < strlength) {

        char buffer[3] = {0,0,0};

        short bufferLength = 0;

        while (bufferLength < 3 && i < strlength)

        buffer[bufferLength++] = source[i++];

        characters[length++] = base64[(buffer[0] & 0xFC) >> 2];

        characters[length++] = base64[((buffer[0] & 0x03) << 4) | ((buffer[1] & 0xF0) >> 4)];

        if (bufferLength > 1)

        characters[length++] = base64[((buffer[1] & 0x0F) << 2) | ((buffer[2] & 0xC0) >> 6)];

        else characters[length++] = '=';

        if (bufferLength > 2)

        characters[length++] = base64[buffer[2] & 0x3F];

        else characters[length++] = '=';

    }

    NSString *g = [[NSString alloc] initWithBytesNoCopy:characters length:length encoding:NSASCIIStringEncoding freeWhenDone:YES];


    return g;

}



@end

AES+Base64的加密方式到此已经结束了，下面讲一下单纯的AES字符串加密的。

和上面的基本上差不多，写一个NSString的类扩展，命名为AES，创建完如果对的话应该是这样的NSString+AES导入如下头文件

#import "NSData+AES.h"

同样的把加解密的方法写在.h文件中，写完如下

#import <Foundation/Foundation.h>
#import "NSData+AES.h"

@interface NSString (AES)

//加密
- (NSString *) AES256_Encrypt:(NSString *)key;

//解密
- (NSString *) AES256_Decrypt:(NSString *)key;

@end

.m实现方法

//加密
- (NSString *) AES256_Encrypt:(NSString *)key{
    const char *cstr = [self cStringUsingEncoding:NSUTF8StringEncoding];
    NSData *data = [NSData dataWithBytes:cstr length:self.length];
    //对数据进行加密
    NSData *result = [data AES256_Encrypt:key];

    //转换为2进制字符串
    if (result && result.length > 0) {

    Byte *datas = (Byte*)[result bytes];
    NSMutableString *output = [NSMutableString stringWithCapacity:result.length * 2];
    for(int i = 0; i < result.length; i++){
        [output appendFormat:@"%02x", datas[i]];
    }
    return output;
    }
    return nil;
}

//解密
- (NSString *) AES256_Decrypt:(NSString *)key{
    //转换为2进制Data
    NSMutableData *data = [NSMutableData dataWithCapacity:self.length / 2];
    unsigned char whole_byte;
    char byte_chars[3] = {'\0','\0','\0'};
    int i;
    for (i=0; i < [self length] / 2; i++) {
    byte_chars[0] = [self characterAtIndex:i*2];
    byte_chars[1] = [self characterAtIndex:i*2+1];
    whole_byte = strtol(byte_chars, NULL, 16);
    [data appendBytes:&whole_byte length:1];
    }

    //对数据进行解密
    NSData* result = [data AES256_Decrypt:key];
    if (result && result.length > 0) {
        return [[NSString alloc] initWithData:result encoding:NSUTF8StringEncoding];
    }
    return nil;
}

到此我们加密的文件基本上都已经OK了，下面我们来简单的的使用一下，具体如下：

#import "ViewController.h"
#import "NSString+AES.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.

    //字符串加密
    NSString *key = @"12345678";//Key是和后台约定的key哦，不然无法解密....

    NSString *secret = @"aes Bison base64";


    NSLog(@"字符串加密---%@",[secret AES256_Encrypt:key]);

    //字符串解密
    NSLog(@"字符串解密---%@",[[secret AES256_Encrypt:key] AES256_Decrypt:key]);


    //NSData加密+base64

    NSData *plain = [secret dataUsingEncoding:NSUTF8StringEncoding];

    NSData *cipher = [plain AES256_Encrypt:key];

    NSLog(@"NSData加密+base64++++%@",[cipher newStringInBase64FromData]);


    //解密

    plain = [cipher AES256_Decrypt:key];

    NSLog(@"NSData解密+base64++++%@", [[NSString alloc] initWithData:plain encoding:NSUTF8StringEncoding]);

}


@end

运行得到打印的结果如下：

2016-03-30 17:31:55.686 AES_256[14242:198853] 字符串加密---07815ca46d20acc3ba4e43d6930c7537496e851a36dbeac34fa30c5796089b02
2016-03-30 17:31:55.687 AES_256[14242:198853] 字符串解密---aes Bison base64
2016-03-30 17:31:55.687 AES_256[14242:198853] NSData加密+base64++++B4FcpG0grMO6TkPWkwx1N0luhRo22+rDT6MMV5YImwI
2016-03-30 17:31:55.687 AES_256[14242:198853] NSData解密+base64++++aes Bison base64