XOR'ing two hex values stored as an NSString?

Question

here is yet another silly question from me!

NSString *hex1 = @"50be4f3de4";
NSString *hex2 = @"30bf69a299";

/* some stuff like result = hex1^hex2;    */

NSString *result = @"6001269f7d";

I have a hex value as a string, stored in two diff. variables. i need to Xor them and the result should be in another string variables?

i tried them by converting string --> NSData --> bytes array --> xor'ing them ...but i have no success..... thank you in advance...

Answer 1

You have to convert every character to Base16(for hexadecimal) format first.Then you should proceed with XORing those characters.You can use the strtol() function to achieve this purpose.

NSString *hex1 = @"50be4f3de4";
NSString *hex2 = @"30bf69a299";

NSMutableArray *hexArray1 = [self splitStringIntoChars:hex1]; 
NSMutableArray *hexArray2 = [self splitStringIntoChars:hex2]; 

NSMutableString *str = [NSMutableString new];
for (int i=0; i<[hexArray1 count]; i++ )
{
    /*Convert to base 16*/
    int a=(unsigned char)strtol([[hexArray1 objectAtIndex:i] UTF8String], NULL, 16);
    int b=(unsigned char)strtol([[hexArray2 objectAtIndex:i] UTF8String], NULL, 16);

    char encrypted = a ^ b;
    NSLog(@"%x",encrypted);
    [str appendFormat:@"%x",encrypted];        
}
NSLog(@"%@",str);

Utility method that i used to split characters of the string

-(NSMutableArray*)splitStringIntoChars:(NSString*)argStr{
    NSMutableArray *characters = [[NSMutableArray alloc] 
                              initWithCapacity:[argStr length]]; 
    for (int i=0; i < [argStr length]; i++) 
    { 
        NSString *ichar = [NSString stringWithFormat:@"%c", [argStr characterAtIndex:i ]]; 
        [characters addObject:ichar]; 
    } 
    return characters;
}

Hope it helps!!