AES128 in Objective-C -> Test Case fails - objective-c

Question

I try to get a AES128 encryption running with objective-c. However, I don't get the correct output.
This may also be a stupid objective-c error because I'm just starting with this language ;-)
My test case looks like this:
CryptoUtils* crypt = [[CryptoUtils alloc] init];
NSData* plaintext = [#"6bc1bee22e409f96e93d7e117393172a" dataUsingEncoding:NSUTF8StringEncoding];
NSData* key = [#"2b7e151628aed2a6abf7158809cf4f3c" dataUsingEncoding:NSUTF8StringEncoding];
NSData* iv = [#"000102030405060708090A0B0C0D0E0F" dataUsingEncoding:NSUTF8StringEncoding];
NSString* encrypted = [crypt encryptData:plaintext withKey:key andIV:iv];
XCTAssertEqualObjects(#"7649abac8119b246cee98e9b12e9197d", encrypted , #"AES testcase1 not equal");
The encryptData method looks like this:
(NSString *)encryptData:(NSData*)clearText withKey:(NSData*) currentKey andIV:(NSData*) currentIV{
// Buffer for Ciphertext
NSMutableData *cipherData = [NSMutableData dataWithLength:clearText.length + kCCBlockSizeAES128];
size_t cipherLength;
CCCryptorStatus cryptStatus = CCCrypt(kCCEncrypt,
kCCAlgorithmAES128,
kCCOptionPKCS7Padding,
currentKey.bytes,
currentKey.length,
currentIV.bytes,
clearText.bytes,
clearText.length,
cipherData.mutableBytes,
cipherData.length,
&cipherLength);
if(cryptStatus){
NSLog(#"Something terrible during encryption happened!");
} else {
NSLog(#"Ciphertext length: %i", [cipherData length]);
NSString *output=[cipherData description];
output = [output stringByReplacingOccurrencesOfString:#" " withString:#""];
output = [output stringByReplacingOccurrencesOfString:#"<" withString:#""];
output = [output stringByReplacingOccurrencesOfString:#">" withString:#""];
return output;
}
return nil;
}
Now, I'm getting back a wrong 'encrypted' String. Especially, it is a lot to long and I suspect the problem to be the NSData's that I pass to the method. Does anybody have an idea of what I'm doing wrong here?
Thank you

Answer 1

You meantion AES128 in your title, but refer to AES256 in your first paragraph.
It also appears that you are using input data, key and IV values that you do not mean to use.
It appears you want your input data to be 128 bits long (which would align with the block size), but in reality it is 376 bits long. This is technically acceptable, since you use padding, but context clues point to this being an oversight.
For AES128 your input key must be 128 bits long, but your key is 256 bits long. This is incorrect for AES128.
It appears you want your IV to be 128 bits long, but in reality it is 256 bits long. This is incorrect for AES - the IV must have the same length as block size, i.e. 128 bits.
Now, what you want to do instead, is probably:
char bytes[] = {0x6b, 0xc1, 0xbe, 0xe2, 0x2e, 0x40, 0x9f, 0x96, 0xe9, 0x3d, 0x7e, 0x11, 0x73, 0x93, 0x17, 0x2a};
NSData *clearText = [NSData dataWithBytes:&bytes length:16];
char keyBytes[] = {0x2b,0x7e,0x15,0x16,0x28,0xae,0xd2,0xa6,0xab,0xf7,0x15,0x88,0x09,0xcf,0x4f,0x3c};
NSData* currentKey = [NSData dataWithBytes:&keyBytes length:16];
char ivBytes[16] = char ivBytes[16] = {0x00,0x01,0x02,0x03,0x04,0x05,0x06,0x07,0x08,0x09,0x0A,0x0B,0x0C,0x0D,0x0E,0x0F};
NSData* currentIV = [NSData dataWithBytes:&ivBytes length:16];
These changes will give you input, key and IV values with 128 bit length.
After making these changes, output will be:
7649abac8119b246cee98e9b12e9197d8964e0b149c10b7b682e6e39aaeb731c00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
The first 32 characters match those you provided. This suggests that your reference value is incomplete, and the code is working as intended.