在目标 c 中，如何使用 md5 作为密钥进行 AES256 加密?

Question

我一直在尝试复制一个安卓代码，该代码使用 md5 作为密钥进行 AES256 加密。一切似乎都很好，但加密后的值似乎不一样。请浏览我的以下代码

人造人：-

public static String encrypt(String key, String value) {
try {
byte[] keyArr = new byte[32];
MessageDigest md = MessageDigest.getInstance("MD5");
byte[] hash = md.digest(key.getBytes("US-ASCII"));//in md5 function 1st line
keyArr = arrayCopy(0, hash, 0, keyArr, 16);//in md5 function 1st for loop
keyArr = arrayCopy(0, hash, 15, keyArr, 16);//in md5 function 2nd for loop
SecretKeySpec skeySpec = new SecretKeySpec(keyArr, "AES");
Cipher cipher = Cipher.getInstance("AES");
cipher.init(Cipher.ENCRYPT_MODE, skeySpec);
byte[] encrypted = cipher.doFinal(value.getBytes());
String encryptedB64 = new String(Base64.encode(encrypted, Base64.DEFAULT));
return encryptedB64;
} catch (Exception ex) {
ex.printStackTrace();
}
return null;
}
private static byte[] arrayCopy(int sourceIndex,byte[] source,int targetIndex,byte[] target,int transferSize){
if(!(transferSize >0))
return null;
if(sourceIndex>=0 && sourceIndex < source.length){
int transferCnt=0;
int i=sourceIndex;
for(int j=targetIndex;;j++,i++){
if(targetIndex>=target.length || sourceIndex>=source.length || (++transferCnt>transferSize)){
break;
}
target[j] = source[i];
}
}else{
return null;
}
return target;
}

iOS objective-c

+ (NSString *) getFalconEncryptedValueForKey:(NSString *)theKey forString:(NSString *)theString
{
char keyPtr[kCCKeySizeAES256+1]; // room for terminator (unused)
bzero(keyPtr, sizeof(keyPtr)); // fill with zeroes (for padding)
NSData *rawData = [theString dataUsingEncoding:NSUTF8StringEncoding];
NSString *md5Key = [self md5:theKey];
[md5Key getCString:keyPtr maxLength:sizeof(keyPtr) encoding:NSUTF8StringEncoding];
NSUInteger dataLength = [rawData length];
size_t bufferSize = dataLength + kCCBlockSizeAES128;
void *buffer = malloc(bufferSize);
size_t numBytesEncrypted = 0;
CCCryptorStatus cryptStatus = CCCrypt(kCCEncrypt, kCCAlgorithmAES128, kCCOptionPKCS7Padding + kCCOptionECBMode,
keyPtr, kCCKeySizeAES256,
NULL /* initialization vector (optional) */,
[rawData bytes], dataLength, /* input */
buffer, bufferSize, /* output */
&numBytesEncrypted);
if (cryptStatus == kCCSuccess)
{
NSData *tempData = [NSData dataWithBytesNoCopy:buffer length:numBytesEncrypted];
NSString* encrypted64 = [tempData base64EncodedStringWithOptions:0];//Even i have tried base 64 encding with other options available
return encrypted64;
}
free(buffer); //free the buffer;
return nil;
}

+ (NSString *) md5:(NSString *) input
{
//    const char * pointer = [self UTF8String];
const char *cStr = [input cStringUsingEncoding:NSASCIIStringEncoding];
unsigned char result[CC_MD5_DIGEST_LENGTH];
CC_MD5( cStr, (CC_LONG)strlen(cStr), result );
NSMutableString *md5String = [NSMutableString stringWithCapacity:CC_MD5_DIGEST_LENGTH * 2];
for (int i = 0; i < CC_MD5_DIGEST_LENGTH; i++)
[md5String appendFormat:@"%02x",result[i]];
for (int i = 0; i < CC_MD5_DIGEST_LENGTH; i++)
[md5String appendFormat:@"%02x",result[i]];
return md5String;
//for 32 byte. md5 produces only 16 byte info. we are replicating it again to make it 32 byte for aes256
}

在我做错的事情上，任何方向都会非常有帮助。提前致谢

Answer 1

使用

md5 的 AES256 加密加倍作为密钥

不，事实并非如此。

在 Android 中，keyArr中第一个hash的最后一个字节被第二个hash(更准确地说是第二个hash的第一个字节(覆盖。因此，keyArr的最后一个字节始终为 0。

我不精通Objective-C，但我认为，这应该做到：

NSMutableString *md5String = [NSMutableString stringWithCapacity:CC_MD5_DIGEST_LENGTH * 2];
for (int i = 0; i < CC_MD5_DIGEST_LENGTH-1; i++)
[md5String appendFormat:@"%02x",result[i]];
for (int i = 0; i < CC_MD5_DIGEST_LENGTH; i++)
[md5String appendFormat:@"%02x",result[i]];
[md5String appendFormat:@"%02x",0];

(顺便说一句，arrayCopy可以生成一个IndexOutOfBoundsException，尽管它有很多检查(。

当然，这会生成一个长度为 64 个字符的十六进制编码字符串。这不是你想要的。相反，您应该生成长度为 32 的实际字节。

正确的代码(通过 OP(

+ (NSString *) getEncryptedValueWithKey:(NSString *)theKey forString:(NSString *)theString
{
NSData *rawData = [theString dataUsingEncoding:NSUTF8StringEncoding];
unsigned char md5Buffer[kCCKeySizeAES256+1];
memset(md5Buffer, 0, kCCKeySizeAES256+1);
const char *cStr = [theKey UTF8String];
// do md5 hashing
CC_MD5(cStr, CC_MD5_DIGEST_LENGTH, md5Buffer);
unsigned char lastChar = md5Buffer[15];
for (NSInteger i = 15; i <= 30; i++) {
md5Buffer[i] = md5Buffer[i-15];
}
md5Buffer[30] = lastChar;
//MD5 key obtaining end
NSUInteger dataLength = [rawData length];
size_t bufferSize = dataLength + kCCBlockSizeAES128;
void *buffer = malloc(bufferSize);
size_t numBytesEncrypted = 0;
CCCryptorStatus cryptStatus = CCCrypt(kCCEncrypt, kCCAlgorithmAES128, kCCOptionPKCS7Padding + kCCOptionECBMode, md5Buffer, kCCKeySizeAES256, NULL /* initialization vector (optional) */, [rawData bytes], dataLength, /* input */ buffer, bufferSize, /* output */ &numBytesEncrypted);
if (cryptStatus == kCCSuccess)
{
NSData *tempData = [NSData dataWithBytesNoCopy:buffer length:numBytesEncrypted];
NSString* encrypted64 = [tempData base64EncodedStringWithOptions:0];//Even i have tried base 64 encding with other options available
return encrypted64;
}
free(buffer); //free the buffer;
return nil;
}