CODEWITHSUNDEEP
iosobjective-cencryptionaescommoncrypto
YYfim
YYfim

Reputation: 1412

Data encryption with AES

I'm building an app that will communicate with a server (php), and this communication (probably will be with json) i want to encrypt. After a lot of searching and reading i found the AESCrypt-Objc project. While testing the encryption (i'm using a web tool AES Encryption test) i found that in the encryption result i'm missing 16 byte of data. Here's the example i'm using In the AES project:

String to be encrypted: "The quick brown fox jumped over the lazy dog". Password: "12345678901234561234567890123456"

The result:

<7eda336b 82f3e279 ae7638fe cccfffc6 5fbef8da 6df76d97 67d8cfa8 5bce2ae9>

My Code:

self.strnToBeEnc = @"The quick brown fox jumped over the lazy dog";
self.appKey      = @"12345678901234561234567890123456";
NSData *data2    = [self.strnToBeEnc dataUsingEncoding:NSUTF8StringEncoding];
NSLog(@"%@", data2); 
NSData *s2 = [data2 AES256EncryptedDataUsingKey:self.appKey error:nil]; 
NSLog(@"%@", s2);

WEB Tool:

Same string and password

The result:

<7eda336b 82f3e279 ae7638fe cccfffc6 5fbef8da 6df76d97 67d8cfa8 5bce2ae9 ca2ed34a 48f85af2 909654d5 b0de0fb7>

As you can see i'm missing some bytes...:) I've tried adding to the buffer in the algorithm, but with no success.

Any advice? Thanks

(if the question is not Detailed enough please let me know)

Upvotes: 3

Views: 562

Answers (1)

dtrotzjr
dtrotzjr

Reputation: 945

I know you were trying to avoid this but I think you might need to spend some time in the source code of AESCrypt-Objc as I suspect it is somehow not encrypting the last block.

Step into the code and see if you actually get to the CCCryptorFinal call, and note its results. This can be found in the AESCrypt-ObjC/NSData+CommonCrypto.m _runCryptor:result: . Another thing to look into is the default padding type they are using which appears to be kCCOptionPKCS7Padding this will also have an effect on your ending bytes.

Do your testing first with non-arbitrary length bytes that are multiples of the AES block size, then once you have validated that move on to the variable length ones you have here.

Upvotes: 1

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