前言:
在我们开发中免不了和服务器做一些数据交互，在交互过程中走得都是http请求，这类请求不像https那样的安全所以就会在交互过程中做一些数据加密解密的事情，现在主流的加密是AES对称加密和RSA非对称加密下面给大家讲解下AES加密，非对称加密会过几天跟新。
AES加密介绍：
- AES加密是一种对称加密方式，他有基本的五种加密模式组成分别是：
1.电码本模式（Electronic Codebook Book (ECB)）；
2.密码分组链接模式（Cipher Block Chaining (CBC)）；
3.计算器模式（Counter (CTR)）；
4.密码反馈模式（Cipher FeedBack (CFB)）；
5.输出反馈模式（Output FeedBack (OFB)）
- 以上所说的这五种加密模式我们讲最常用的CBC模式，下面我说一下实现AES对称加密(CBC)的基本步骤;
1.要加密的密文转为NSData类型
2.使用AES对称加密(CBC)加密NSData
3.之后对加密过后的NSData进行编码(编码在下面我会说到)
AES加密代码实现：
新建SecurityUtil继承NSObject
SecurityUtil.h实现：
#pragma mark - AES加密
//将string转成带密码的data
+ (NSString*)encryptAESData:(NSString*)string Withkey:(NSString * )key ivkey:(NSString * )ivkey;
//将带密码的data转成string
+(NSString*)decryptAESData:(NSString*)data Withkey:(NSString *)key ivkey:(NSString * )ivkey;
SecurityUtil.m实现(加密部分)：
#pragma mark - AES加密
//将string转成带密码的data
+(NSString*)encryptAESData:(NSString*)string Withkey:(NSString *)key ivkey:(NSString *)ivkey
{
//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 ivKey:ivkey];
//加密之后编码
return [self dataTohexString:encryptedData];;
}
#pragma mark - AES解密
//将带密码的data转成string
+(NSString*)decryptAESData:(NSString*)string Withkey:(NSString *)key ivkey:(NSString *)ivkey
{
//对数据进行解密
NSData* result = [[self hexStringToData:string] AES128DecryptWithKey:key ivkey:ivkey];
if (result && result.length > 0) {
//加密之后进行编码
return [[NSString alloc] initWithData:result encoding:NSUTF8StringEncoding];
}
return nil;
}
SecurityUtil.m实现(编码部分)：
#pragma mark - 16位编码 -加密
+ (NSString *)dataTohexString:(NSData*)data
{
Byte *bytes = (Byte *)[data bytes];
NSString *hexStr=@"";
for(int i=0;i<[data length];i++)
{
NSString *newHexStr = [NSString stringWithFormat:@"%x",bytes[i]&0xff];//16进制数
if([newHexStr length]==1)
hexStr = [NSString stringWithFormat:@"%@0%@",hexStr,newHexStr];
else
hexStr = [NSString stringWithFormat:@"%@%@",hexStr,newHexStr];
}
return hexStr;
}
#pragma mark - 16位编码 -解密
+ (NSData*)hexStringToData:(NSString*)hexString
{
int j=0;
Byte bytes[hexString.length]; ///3ds key的Byte 数组， 128位
for(int i=0;i<[hexString length];i++)
{
int int_ch; /// 两位16进制数转化后的10进制数
unichar hex_char1 = [hexString characterAtIndex:i]; ////两位16进制数中的第一位(高位*16)
int int_ch1;
if(hex_char1 >= '0' && hex_char1 <='9')
int_ch1 = (hex_char1-48)*16; //// 0 的Ascll - 48
else if(hex_char1 >= 'A' && hex_char1 <='F')
int_ch1 = (hex_char1-55)*16; //// A 的Ascll - 65
else
int_ch1 = (hex_char1-87)*16; //// a 的Ascll - 97
i++;
unichar hex_char2 = [hexString characterAtIndex:i]; ///两位16进制数中的第二位(低位)
int int_ch2;
if(hex_char2 >= '0' && hex_char2 <='9')
int_ch2 = (hex_char2-48); //// 0 的Ascll - 48
else if(hex_char1 >= 'A' && hex_char1 <='F')
int_ch2 = hex_char2-55; //// A 的Ascll - 65
else
int_ch2 = hex_char2-87; //// a 的Ascll - 97
int_ch = int_ch1+int_ch2;
//NSLog(@"int_ch=%x",int_ch);
bytes[j] = int_ch; ///将转化后的数放入Byte数组里
j++;
}
// NSData *newData = [[NSData alloc] initWithBytes:bytes length:j];
NSData *newData = [[NSData alloc] initWithBytes:bytes length:j];
//NSLog(@"newData=%@",newData);
return newData;
}
新建一个NSData的扩展咋们把他命名为AES
NSData+AES.h实现：
@class NSString;
@interface NSData (Encryption)
- (NSData *)AES128EncryptWithKey:(NSString *) key ivKey:(NSString *)ivkey;//加密
- (NSData *)AES128DecryptWithKey:(NSString *) key ivkey:(NSString * )ivkey;//解密
NSData+AES.m实现：
//(key和iv向量这里是16位的) 这里是CBC加密模式，安全性更高
//加密
- (NSData *)AES128EncryptWithKey:(NSString *) key ivKey:(NSString *)ivkey{
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 ,
keyPtr, kCCBlockSizeAES128,
[ivkey UTF8String],
[self bytes], dataLength,
buffer, bufferSize,
&numBytesEncrypted);
if (cryptStatus == kCCSuccess) {
return [NSData dataWithBytesNoCopy:buffer length:numBytesEncrypted];
}
free(buffer);
return nil;
}
//解密
- (NSData *)AES128DecryptWithKey:(NSString *) key ivkey:(NSString *)ivkey {
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 ,
keyPtr, kCCBlockSizeAES128,
[ivkey UTF8String],
[self bytes], dataLength,
buffer, bufferSize,
&numBytesDecrypted);
if (cryptStatus == kCCSuccess) {
return [NSData dataWithBytesNoCopy:buffer length:numBytesDecrypted];
}
free(buffer);
return nil;
}
- 试验调用一下:
NSString *originalString = @"加密这个字符串";
NSString * secretStr = @"秘钥是这个";
//CBC加密字符串
NSString * encryptCBC = [SecurityUtil encryptAESData: originalString Withkey:uuid ivkey: secretStr];
//CBC解密字符串
NSString * decryptCBC = [SecurityUtil decryptAESData: encryptCBC Withkey:uuid ivkey: secretStr];
- AES加密(CBC)全部实现我们已经做好了下面我讲一下编码;
编码有很多种在我的项目中我们采用了16位编码，为什么说我要采用16位编码这又要讲到Base64编码，首先我先给大家看下这俩种编码后的密文是什么样子的。。
Base64编码：
BsDhzys9BkPbfuMUK4SDpSqh47FMMNltY6huj/lMwI77ibB61Wk9eBMMzQRmNgVvmnbTpWKNUdS2XXKgfwuEyGjJC7uUSkoTuV/TFN+BEFv3vlL0UKeY1Jt8plcJzrDKyDxK0oQOiM9THr5ZTFOsdDGfM3cmGWf7KRTQFwYE=
16位编码：
06C0E1CF2B3D0643DB7EE3142B8483A52AA1E3B14C33FA21365B58EA1BA3FE533023BEE26C1EB55A4F5E04C33341198D815BE69DB4E958A354752D975CA81FC2E1321A3242EEE5129284EE57F4C537E04416FDEF94BD1429E63526DF2995C273AC32B20F12B4A103A233D4C7AF965314EB1D0C67CCDDC98659FECA453405C181
大家也看到了俩种编码之后的密文明显的不同之处，Base64的唯一缺点就是其中有很多的特殊符号这种特殊符号在http传送过程中会发生改变导致密文解码解不了，所以我就采用了16位编码避免这种事情的发生。
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