前段时间做了AES256加密解密，怕过段时间忘了，现在赶紧过来补一下。
1.先来说说解密，因为我们项目后台人员做的加密，他返回的数据是加密的数据，所以我主要做了解密。
NSData *base = [[NSData alloc]initWithBase64EncodedString:str options:0];
NSData*abc = [base AES256DecryptWithKey:de];
这两句代码就是核心代码了，第一句是base64编码(我会在另一篇文章里面单独介绍的)
- (NSData *)AES256DecryptWithKey:(NSString *)key {
// 'key' should be 32 bytes for AES256, will be null-padded otherwise
// 中文翻译（翻译的不太好勿怪）意思是AES256 它解密的key应该是占32个字节不够的话用0填充
// 创建一个数组 kCCKeySizeAES256代表一个数值32 意思是此数组能够存33个字符
char keyPtr[kCCKeySizeAES256+1]; // room for terminator (unused)
// 下面这句意思不够 用0填充
bzero(keyPtr, sizeof(keyPtr)); // fill with zeroes (for padding)
// fetch key data (获取关键数据)
[key getCString:keyPtr maxLength:sizeof(keyPtr) encoding:NSUTF8StringEncoding];
// 这里的self 代表调用这个方法的NSData 对象 计算大小
NSUInteger dataLength = [self length];
// 块加密，输出的大小总是小于或等于输入大小加上一个块的大小.这就是为什么我们需要在这里添加一个块的大小
//See the doc: For block ciphers, the output size will always be less than or
//equal to the input size plus the size of one block.
//That's why we need to add the size of one block here
size_t bufferSize = dataLength + kCCBlockSizeAES128;
void *buffer = malloc(bufferSize);
size_t numBytesDecrypted = 0;
CCCryptorStatus cryptStatus = CCCrypt(kCCDecrypt, kCCAlgorithmAES128, kCCOptionPKCS7Padding | kCCOptionECBMode,
keyPtr, kCCKeySizeAES128,
NULL /* initialization vector (optional) */,
[self bytes], dataLength, /* input */
buffer, bufferSize, /* output */
&numBytesDecrypted);
if (cryptStatus == kCCSuccess) {
// 返回的NSData拥有自己的缓冲区并将在delloac时释放掉
//the returned NSData takes ownership of the buffer and will free it on deallocation
return [NSData dataWithBytesNoCopy:buffer length:numBytesDecrypted];
}
free(buffer); //free the buffer;
return nil;
}
重点就是介绍加粗的字体了，其实我也就是翻译一下
2.接下来就是加密，加密与解密代码上面大同小异，估计是因为AES256是属于对称加密的原因
NSData *data2 = [data AES256EncryptWithKey:@"此处是16个字符(也就是32个字节)"];
NSString *base64Encoded = [data2 base64EncodedStringWithOptions:0];
因为我们解密的时候是先追加base64编码然后解的密，所以当我们加密的时候，方向就要反过来，先加密然后base64编码。代码附上：
- (NSData *)AES256EncryptWithKey:(NSString *)key {
// 'key' should be 32 bytes for AES256, will be null-padded otherwise
char keyPtr[kCCKeySizeAES128+1]; // room for terminator (unused)
bzero(keyPtr, sizeof(keyPtr)); // fill with zeroes (for padding)
// fetch key data
[key getCString:keyPtr maxLength:sizeof(keyPtr) encoding:NSUTF8StringEncoding];
NSUInteger dataLength = [self length];
//See the doc: For block ciphers, the output size will always be less than or
//equal to the input size plus the size of one block.
//That's why we need to add the size of one block here
size_t bufferSize = dataLength + kCCBlockSizeAES128;
void *buffer = malloc(bufferSize);
size_t numBytesEncrypted = 0;
CCCryptorStatus cryptStatus = CCCrypt(kCCEncrypt, kCCAlgorithmAES128, kCCOptionPKCS7Padding | kCCOptionECBMode,
keyPtr, kCCKeySizeAES128,
NULL /* initialization vector (optional) */,
[self bytes], dataLength, /* input */
buffer, bufferSize, /* output */
&numBytesEncrypted);
if (cryptStatus == kCCSuccess) {
//the returned NSData takes ownership of the buffer and will free it on deallocation
return [NSData dataWithBytesNoCopy:buffer length:numBytesEncrypted];
}
free(buffer); //free the buffer;
return nil;
}
最后你只需要把方法名写到.h中就可以愉快的使用了
