How to use hex decimal key with AES encryption? - objective-c

Question

My question is I need to use the following hexadecimal key to encrypt but it assumes it as a string?
key = 0x11,0x11,0x11,0x11,0x11,0x11,0x11,0x11,0x11,0x11,0x11,0x11,0x11,0x11,0x11,0x11
I had tried using [key bytes] instead of keyptr in the CCrypt function but it does't work...
- (NSData *)AES128EncryptWithKey:(NSString *)key theData:(NSData *)Data {
// 'key' should be 32 bytes for AES256, will be null-padded otherwise
char keyPtr[kCCKeySizeAES128]={'1'};; // room for terminator (unused) // oorspronkelijk 256
bzero(keyPtr, sizeof(keyPtr)); // fill with zeroes (for padding)
// fetch key data
[key getCString:keyPtr maxLength:sizeof(keyPtr) encoding:NSUTF8StringEncoding];
NSLog(#"keyPtr %s",keyPtr);
NSUInteger dataLength = [Data 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, kCCOptionECBMode,
keyPtr,
kCCKeySizeAES128, // oorspronkelijk 256
nil, /* initialization vector (optional) */
[Data bytes],
dataLength, /* input */
buffer,
bufferSize, /* output */
&numBytesEncrypted);
if (cryptStatus == kCCSuccess) {
NSLog(#"Encrypt SUCCESS");
//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;
}
- (NSData *)AES128DecryptWithKey:(NSString *)key theData:(NSData *)Data{
// 'key' should be 32 bytes for AES256, will be null-padded otherwise
char keyPtr[kCCKeySizeAES128+1]; // room for terminator (unused) // oorspronkelijk 256
bzero(keyPtr, sizeof(keyPtr)); // fill with zeroes (for padding)
// fetch key data
[key getCString:keyPtr maxLength:sizeof(keyPtr) encoding:NSASCIIStringEncoding];
NSUInteger dataLength = [Data 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 numBytesDecrypted = 0;
CCCryptorStatus cryptStatus = CCCrypt(kCCDecrypt, kCCAlgorithmAES128, kCCOptionECBMode+kCCOptionPKCS7Padding,
keyPtr, kCCKeySizeAES128, // oorspronkelijk 256
NULL /* initialization vector (optional) */,
[Data bytes], dataLength, /* input */
buffer, bufferSize, /* output */
&numBytesDecrypted);
if (cryptStatus == kCCSuccess) {
NSLog(#"Decrypt SUCCESS");
//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;
}

Answer 1

You can use NSScanner, like this:
NSString *keyStr = #"0x11,0x12,0x13,0x14,0x13,0x1a,0x1b,0x1c,0x1f,0x11,0x11,0x11,0x11,0x11,0x11,0xfe";
NSScanner *scan = [NSScanner scannerWithString:keyStr];
[scan setCharactersToBeSkipped:[NSCharacterSet characterSetWithCharactersInString:#","]];
unsigned int tmp;
char key[16];
for (int i = 0 ; i != 16 ; i++) {
[scan scanHexInt:&tmp];
key[i] = (char)tmp;
}
At this point, the array key contains 16 bytes of your key converted from hex to bytes.