- (NSString *)stringToMD5:(NSString *)input {
    
    const char *cStr = [input UTF8String];
    
    unsigned char digest[CC_MD5_DIGEST_LENGTH];
    
    // This is the md5 call
    CC_MD5( cStr, strlen(cStr), digest );
    
    NSMutableString *output = [NSMutableString stringWithCapacity:CC_MD5_DIGEST_LENGTH * 2];
    
    for(int i = 0; i < CC_MD5_DIGEST_LENGTH; i++)
        [output appendFormat:@"%02x", digest[i]];
    
    return  output;
}