How can I do this same encrypt/decrypt PHP function on iOS with Objective-C?

Question

I have a function in PHP that encrypts and decrypts strings:

function encrypt_decrypt($action, $string) 
{
   $output = false;
   $key = \'mykeyhereblah\';
   $i         


        

Answer 1

So you want to encrypt using AES256 in CBC mode. The library you are looking for is CommonCrypto and you can find a good article about it here:http://robnapier.net/aes-commoncrypto.

You will also need an MD5 function that you can find here: http://www.makebetterthings.com/iphone/how-to-get-md5-and-sha1-in-objective-c-ios-sdk/

Your code should look something like this:

NSString *originalString,*keyString;
NSData *key = [[self md5:keyString] dataUsingEncoding:NSUTF8StringEncoding];
NSData *iv = [[self md5:[self md5:key]] dataUsingEncoding:NSUTF8StringEncoding];
NSData *data = [originalString dataUsingEncoding:NSUTF8StringEncoding];
NSMutableData *cipherData = [NSMutableData dataWithLength:data.length + kCCBlockSizeAES128]; //The block size of MCRYPT_RIJNDAEL_256 is just like AES128
size_t outLength;

CCCryptorStatus result
       = CCCrypt(kCCEncrypt, // operation, replace with kCCDecrypt to decrypt
                 kCCAlgorithmAES, // Same as MCRYPT_RIJNDAEL_256
                 nil, // CBC mode
                 key.bytes, // key
                 32, // Since you are using AES256
                 iv.bytes,// iv
                 data.bytes, // dataIn
                 data.length, // dataInLength,
                 cipherData.mutableBytes, // dataOut
                 cipherData.length, // dataOutAvailable
                 &outLength); // dataOutMoved
NSString resultString = [cipherData base64Encoding];

And make sure you are using the same UTF8 encoding in both cases, and use this import:

#import 

I am pretty sure this should work.

EDIT: the key length should be 32 since you are using AES256 256bit=32bytes. The MD5 output wouldn't match this length by default I think.