How can i make an xcode encrypted string same as encrypted string in java

Question

I am new in xcode. I am encrypting a string in xcode and also encrypting the same string in Java using AES 256 bit and am seeing some strange issues. The Encryption in java and Iphone do not match each other i have used the following code:

NSString *password = @"mypassword";
NSString *str = @"message"; 
NSLog(@"encrypting string =%@",str);
NSData *data = [str dataUsingEncoding: NSASCIIStringEncoding];
NSData *encryptedData = [data AES256EncryptWithKey:password];
NSString *responseString = [[NSString alloc] initWithData:encryptedData encoding:NSASCIIStringEncoding];
[Base64 initialize];
NSString *b64EncStr = [Base64 encode:encryptedData];

NSLog(@"Base 64 encoded = %@",b64EncStr);
NSData  *b64DecData = [Base64 decode:b64EncStr];
NSData *decryptedData = [b64DecData AES256DecryptWithKey:password];
NSString* decryptedStr = [[NSString alloc] initWithData:decryptedData encoding:NSASCIIStringEncoding];
NSLog(@"decrypted string = %@",decryptedStr);

 /////////////////************///////////////***************************/////////////////////

 - (NSData *)AES256EncryptWithKey:(NSString *)key {
char keyPtr[kCCKeySizeAES256 + 1]; 
bzero( keyPtr, sizeof( keyPtr ) ); 
 [key getCString:keyPtr maxLength:sizeof( keyPtr )
 encoding:NSUTF8StringEncoding];
NSUInteger dataLength = [self length];
size_t bufferSize = dataLength + kCCBlockSizeAES128;
void *buffer = malloc( bufferSize );

size_t numBytesEncrypted = 0;
CCCryptorStatus cryptStatus = CCCrypt( kCCEncrypt, kCCAlgorithmAES128, kCCOptionPKCS7Padding,
                                           keyPtr, kCCKeySizeAES256,
                                           NULL ,
                                           [self bytes], dataLength, 
                                           buffer, bufferSize, 
                                           &numBytesEncrypted );
    if( cryptStatus == kCCSuccess )    {
       return [NSData dataWithBytesNoCopy:buffer
 length:numBytesEncrypted];    }

    >free( buffer ); 
    >return nil; }




- (NSData *)AES256DecryptWithKey:(NSString *)key {
char keyPtr[kCCKeySizeAES256+1]; 
bzero( keyPtr, sizeof( keyPtr ) ); 
[key getCString:keyPtr maxLength:sizeof( keyPtr )
 encoding:NSUTF8StringEncoding];

    NSUInteger dataLength = [self length];
size_t bufferSize = dataLength + kCCBlockSizeAES128;
void *buffer = malloc( bufferSize );
 size_t numBytesDecrypted = 0;
 CCCryptorStatus cryptStatus = CCCrypt( kCCDecrypt,
 kCCAlgorithmAES128, kCCOptionPKCS7Padding,
                                           keyPtr, kCCKeySizeAES256,
                                           NULL ,
                                           [self bytes], dataLength, 
                                           buffer, bufferSize, 
                                           &numBytesDecrypted );

    if( cryptStatus == kCCSuccess )    {
       return [NSData dataWithBytesNoCopy:buffer
 length:numBytesDecrypted];    }

 free( buffer ); 
 return nil; }

i am getting an encrypted string nd1+bWMbk+BEnr9uPIq2eQ== in xcode

but in java using the following code i am encrypting it

SecretKeySpec spec = getKeySpec();
Cipher cipher = Cipher.getInstance("AES");
cipher.init(Cipher.ENCRYPT_MODE, spec);
BASE64Encoder enc = new BASE64Encoder();
String hexString = stringToHex(text);
>return enc.encode(cipher.doFinal(hex2byte(hexString)));

and the encrypted string is mCP+z7ZqxDWPoJPaPoVfSw== i am not able to find the perfect solution in java?

Please edit your post and use the "code sample" button rather than the "bockquote" button to format your code. It's unreadable as is. — JB Nizet
– JB Nizet, Commented Sep 8, 2011 at 7:10

rossum · Accepted Answer · 2011-09-08 10:16:49Z

1

I have added the encryption tag. You need to be sure that both sides are the same. Both sides must use AES-256 in the same mode (use CBC mode) with the same key, the same IV (you may need to pass it across) and the same padding (use PKCS7).

If you rely on defaults then you will find that the defaults differ any you will get different results.

You are also using text strings. You further need to be sure that both sides are using the same text encoding, preferably UTF-8. It might be easier to check things using byte arrays first, so as to eliminate possible problems with text handling. You can always add the text back in later once you have got the byte arrays working correctly.

answered Sep 8, 2011 at 10:16

rossum

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