LOOCryptString.h

//
//  LOOCryptString.h
//
//  Created by Marcin Swiderski on 6/8/12.
//  Copyright (c) 2012 Marcin Swiderski. All rights reserved.
//
//  This software is provided 'as-is', without any express or implied
//  warranty.  In no event will the authors be held liable for any damages
//  arising from the use of this software.
//  
//  Permission is granted to anyone to use this software for any purpose,
//  including commercial applications, and to alter it and redistribute it
//  freely, subject to the following restrictions:
//  
//  1. The origin of this software must not be misrepresented; you must not
//     claim that you wrote the original software. If you use this software
//     in a product, an acknowledgment in the product documentation would be
//     appreciated but is not required.
//  2. Altered source versions must be plainly marked as such, and must not be
//     misrepresented as being the original software.
//  3. This notice may not be removed or altered from any source distribution.
//
//
// USAGE: To hide the string you just have to surround it with a macro like this:
// 
//     NSString *secret = LOO_CRYPT_STR_N("A7LZ14F88Y", 10);
// 
// Remember to use C-sting, because NSString literals cannot be processed in compile time.
//
// IMPORTANT: Works with -Os (Fastest, Smallest) optimization level.

// __str - C-string.
// __n - Number of characters in string (without trailing \0 character).
#define LOO_CRYPT_STR_N(__str, __n) LOODecrypStrN((const unsigned char []){ LOO_ENCRYPT_STR_TO_CHAR_##__n(__str) }, __n + 1)

// This is not very good encryption macro. You should change it for something stronger probably.
#define LOO_ENCRYPT_STR_CHAR_AT(__str, __i) ((unsigned char)(__str[__i]) ^ 0xFF)

// This must match LOO_ENCRYPT_STR_CHAR_AT.
NSString *LOODecrypStrN(const unsigned char encStr[], size_t n);

#define LOO_ENCRYPT_STR_TO_CHAR_0(__str)  LOO_ENCRYPT_STR_CHAR_AT(__str, 0)
#define LOO_ENCRYPT_STR_TO_CHAR_1(__str)  LOO_ENCRYPT_STR_TO_CHAR_0(__str),  LOO_ENCRYPT_STR_CHAR_AT(__str, 1)
#define LOO_ENCRYPT_STR_TO_CHAR_2(__str)  LOO_ENCRYPT_STR_TO_CHAR_1(__str),  LOO_ENCRYPT_STR_CHAR_AT(__str, 2)
#define LOO_ENCRYPT_STR_TO_CHAR_3(__str)  LOO_ENCRYPT_STR_TO_CHAR_2(__str),  LOO_ENCRYPT_STR_CHAR_AT(__str, 3)
#define LOO_ENCRYPT_STR_TO_CHAR_4(__str)  LOO_ENCRYPT_STR_TO_CHAR_3(__str),  LOO_ENCRYPT_STR_CHAR_AT(__str, 4)
#define LOO_ENCRYPT_STR_TO_CHAR_5(__str)  LOO_ENCRYPT_STR_TO_CHAR_4(__str),  LOO_ENCRYPT_STR_CHAR_AT(__str, 5)
#define LOO_ENCRYPT_STR_TO_CHAR_6(__str)  LOO_ENCRYPT_STR_TO_CHAR_5(__str),  LOO_ENCRYPT_STR_CHAR_AT(__str, 6)
#define LOO_ENCRYPT_STR_TO_CHAR_7(__str)  LOO_ENCRYPT_STR_TO_CHAR_6(__str),  LOO_ENCRYPT_STR_CHAR_AT(__str, 7)
#define LOO_ENCRYPT_STR_TO_CHAR_8(__str)  LOO_ENCRYPT_STR_TO_CHAR_7(__str),  LOO_ENCRYPT_STR_CHAR_AT(__str, 8)
#define LOO_ENCRYPT_STR_TO_CHAR_9(__str)  LOO_ENCRYPT_STR_TO_CHAR_8(__str),  LOO_ENCRYPT_STR_CHAR_AT(__str, 9)
#define LOO_ENCRYPT_STR_TO_CHAR_10(__str) LOO_ENCRYPT_STR_TO_CHAR_9(__str),  LOO_ENCRYPT_STR_CHAR_AT(__str, 10)
#define LOO_ENCRYPT_STR_TO_CHAR_11(__str) LOO_ENCRYPT_STR_TO_CHAR_10(__str), LOO_ENCRYPT_STR_CHAR_AT(__str, 11)
#define LOO_ENCRYPT_STR_TO_CHAR_12(__str) LOO_ENCRYPT_STR_TO_CHAR_11(__str), LOO_ENCRYPT_STR_CHAR_AT(__str, 12)
#define LOO_ENCRYPT_STR_TO_CHAR_13(__str) LOO_ENCRYPT_STR_TO_CHAR_12(__str), LOO_ENCRYPT_STR_CHAR_AT(__str, 13)
#define LOO_ENCRYPT_STR_TO_CHAR_14(__str) LOO_ENCRYPT_STR_TO_CHAR_13(__str), LOO_ENCRYPT_STR_CHAR_AT(__str, 14)
#define LOO_ENCRYPT_STR_TO_CHAR_15(__str) LOO_ENCRYPT_STR_TO_CHAR_14(__str), LOO_ENCRYPT_STR_CHAR_AT(__str, 15)
#define LOO_ENCRYPT_STR_TO_CHAR_16(__str) LOO_ENCRYPT_STR_TO_CHAR_15(__str), LOO_ENCRYPT_STR_CHAR_AT(__str, 16)
#define LOO_ENCRYPT_STR_TO_CHAR_17(__str) LOO_ENCRYPT_STR_TO_CHAR_16(__str), LOO_ENCRYPT_STR_CHAR_AT(__str, 17)
#define LOO_ENCRYPT_STR_TO_CHAR_18(__str) LOO_ENCRYPT_STR_TO_CHAR_17(__str), LOO_ENCRYPT_STR_CHAR_AT(__str, 18)
#define LOO_ENCRYPT_STR_TO_CHAR_19(__str) LOO_ENCRYPT_STR_TO_CHAR_18(__str), LOO_ENCRYPT_STR_CHAR_AT(__str, 19)
#define LOO_ENCRYPT_STR_TO_CHAR_20(__str) LOO_ENCRYPT_STR_TO_CHAR_19(__str), LOO_ENCRYPT_STR_CHAR_AT(__str, 20)
#define LOO_ENCRYPT_STR_TO_CHAR_21(__str) LOO_ENCRYPT_STR_TO_CHAR_20(__str), LOO_ENCRYPT_STR_CHAR_AT(__str, 21)
#define LOO_ENCRYPT_STR_TO_CHAR_22(__str) LOO_ENCRYPT_STR_TO_CHAR_21(__str), LOO_ENCRYPT_STR_CHAR_AT(__str, 22)
#define LOO_ENCRYPT_STR_TO_CHAR_23(__str) LOO_ENCRYPT_STR_TO_CHAR_22(__str), LOO_ENCRYPT_STR_CHAR_AT(__str, 23)
#define LOO_ENCRYPT_STR_TO_CHAR_24(__str) LOO_ENCRYPT_STR_TO_CHAR_23(__str), LOO_ENCRYPT_STR_CHAR_AT(__str, 24)
#define LOO_ENCRYPT_STR_TO_CHAR_25(__str) LOO_ENCRYPT_STR_TO_CHAR_24(__str), LOO_ENCRYPT_STR_CHAR_AT(__str, 25)
#define LOO_ENCRYPT_STR_TO_CHAR_26(__str) LOO_ENCRYPT_STR_TO_CHAR_25(__str), LOO_ENCRYPT_STR_CHAR_AT(__str, 26)
#define LOO_ENCRYPT_STR_TO_CHAR_27(__str) LOO_ENCRYPT_STR_TO_CHAR_26(__str), LOO_ENCRYPT_STR_CHAR_AT(__str, 27)
#define LOO_ENCRYPT_STR_TO_CHAR_28(__str) LOO_ENCRYPT_STR_TO_CHAR_27(__str), LOO_ENCRYPT_STR_CHAR_AT(__str, 28)
#define LOO_ENCRYPT_STR_TO_CHAR_29(__str) LOO_ENCRYPT_STR_TO_CHAR_28(__str), LOO_ENCRYPT_STR_CHAR_AT(__str, 29)
#define LOO_ENCRYPT_STR_TO_CHAR_30(__str) LOO_ENCRYPT_STR_TO_CHAR_29(__str), LOO_ENCRYPT_STR_CHAR_AT(__str, 30)
#define LOO_ENCRYPT_STR_TO_CHAR_31(__str) LOO_ENCRYPT_STR_TO_CHAR_30(__str), LOO_ENCRYPT_STR_CHAR_AT(__str, 31)
#define LOO_ENCRYPT_STR_TO_CHAR_32(__str) LOO_ENCRYPT_STR_TO_CHAR_31(__str), LOO_ENCRYPT_STR_CHAR_AT(__str, 32)
#define LOO_ENCRYPT_STR_TO_CHAR_33(__str) LOO_ENCRYPT_STR_TO_CHAR_32(__str), LOO_ENCRYPT_STR_CHAR_AT(__str, 33)
#define LOO_ENCRYPT_STR_TO_CHAR_34(__str) LOO_ENCRYPT_STR_TO_CHAR_33(__str), LOO_ENCRYPT_STR_CHAR_AT(__str, 34)
#define LOO_ENCRYPT_STR_TO_CHAR_35(__str) LOO_ENCRYPT_STR_TO_CHAR_34(__str), LOO_ENCRYPT_STR_CHAR_AT(__str, 35)

// Need more? Type (or better automatically generate) it yourself ;)

LOOCryptString.m

//
//  LOOCryptString.m
//
//  Created by Marcin Swiderski on 6/8/12.
//  Copyright (c) 2012 Marcin Swiderski. All rights reserved.
//
//  This software is provided 'as-is', without any express or implied
//  warranty.  In no event will the authors be held liable for any damages
//  arising from the use of this software.
//  
//  Permission is granted to anyone to use this software for any purpose,
//  including commercial applications, and to alter it and redistribute it
//  freely, subject to the following restrictions:
//  
//  1. The origin of this software must not be misrepresented; you must not
//     claim that you wrote the original software. If you use this software
//     in a product, an acknowledgment in the product documentation would be
//     appreciated but is not required.
//  2. Altered source versions must be plainly marked as such, and must not be
//     misrepresented as being the original software.
//  3. This notice may not be removed or altered from any source distribution.
//

#import "LOOCryptString.h"

NSString *LOODecrypStrN(const unsigned char encStr[], size_t n) {
  char *buf = [[NSMutableData dataWithLength:n] mutableBytes];
  for (NSInteger i = 0; i != n; ++i) {
    buf[i] = encStr[i] ^ 0xFF;
  }
  return [NSString stringWithCString:buf encoding:NSASCIIStringEncoding];
}