Decrypt AES128/CBC in Objective-C from PHP

Question

I'm new to xCode and Objective-C. I've coded a QR-Scanner, now I need to decrypt the Data which is encryptet with AES128 CBC. I encrypt the plaintext using this snippet in php: http://www.androidsnippets.com/encrypt-decrypt-between-android-and-php

Could you help me pls? Sorry for my bad English, I'm German :D

Answer 1

Use CommonCrypto, See CommonCrypto and CCCryptor

Here is a snippit to get you started:

+ (NSData *)doCipher:(NSData *)dataIn
                  iv:(NSData *)iv
                 key:(NSData *)symmetricKey
             context:(CCOperation)encryptOrDecrypt
               error:(NSError **)error
{
    CCCryptorStatus ccStatus   = kCCSuccess;
    size_t          cryptBytes = 0;    // Number of bytes moved to buffer.
    NSMutableData  *dataOut    = [NSMutableData dataWithLength:dataIn.length + kCCBlockSizeAES128];

    ccStatus = CCCrypt( encryptOrDecrypt,
                       kCCAlgorithmAES128,
                       kCCOptionPKCS7Padding,
                       symmetricKey.bytes, 
                       kCCKeySizeAES128,
                       iv.bytes,
                       dataIn.bytes,
                       dataIn.length,
                       dataOut.mutableBytes,
                       dataOut.length,
                       &cryptBytes);

    if (ccStatus == kCCSuccess) {
        dataOut.length = cryptBytes;
    }
    else {
        if (error) {
            *error = [NSError errorWithDomain:@"kEncryptionError"
                                         code:ccStatus
                                     userInfo:nil];
        }
        dataOut = nil;
    }

    return dataOut;
}

Also see RNCryptor for a full implementation.