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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
值得注意的是Key是和后台约定的key哦，不然无法解密....
如后台无法解密可尝试一下这篇文章的解决方法ios端解密出现无法解密问题的解决方案
最后留下demo下载地址
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