Objective-C

AES XTS Mode

See more Encryption Examples

Demonstrates the AES-XTS mode of operation.

Note: This example requires Chilkat v9.5.0.91 or greater.

Objective-C

#import <NSString.h>
#import <CkoBinData.h>
#import <CkoCrypt2.h>

BOOL success = NO;

//  This example assumes the Chilkat API to have been previously unlocked.
//  See Global Unlock Sample for sample code.

//  Here we have a sample from CAVS validatition data:

//  COUNT = 301
//  DataUnitLen = 200
//  Key = 
//  394c97881abd989d29c703e48a72b397
//  a7acf51b59649eeea9b33274d8541df4
//  i = 4b15c684a152d485fe9937d39b168c29
//  PT = 2f3b9dcfbae729583b1d1ffdd16bb6fe2757329435662a78f0
//  CT = f3473802e38a3ffef4d4fb8e6aa266ebde553a64528a06463e

//  Note: The above sample requires an AES-XTS implementation that fully supports ciphertext-stealing
//  because the data to be encrypted is not an even multiple of the AES block size (i.e. not a multiple of 16 bytes).
//  Chilkat fully supports AES-XTS with ciphertext stealing.
//  (i.e. Chilkat implements XEX-based tweaked-codebook mode with ciphertext stealing (XTS))

NSString *key = @"394c97881abd989d29c703e48a72b397";
NSString *tweakKey = @"a7acf51b59649eeea9b33274d8541df4";
NSString *dataUnit = @"4b15c684a152d485fe9937d39b168c29";

CkoBinData *bd = [[CkoBinData alloc] init];
[bd AppendEncoded: @"2f3b9dcfbae729583b1d1ffdd16bb6fe2757329435662a78f0" encoding: @"hex"];

CkoCrypt2 *crypt = [[CkoCrypt2 alloc] init];

crypt.CryptAlgorithm = @"aes";
crypt.CipherMode = @"xts";
crypt.KeyLength = [NSNumber numberWithInt:128];

[crypt SetEncodedKey: key encoding: @"hex"];
[crypt XtsSetEncodedTweakKey: tweakKey encoding: @"hex"];
[crypt XtsSetEncodedTweakValue: dataUnit encoding: @"hex"];

//  In-place encrypt the contents of bd.
success = [crypt EncryptBd: bd];

NSLog(@"%@%@",@"CT = ",[bd GetEncoded: @"hexlower"]);

//  Decrypt to revert back to the unencrypted content:
success = [crypt DecryptBd: bd];

NSLog(@"%@%@",@"PT = ",[bd GetEncoded: @"hexlower"]);

//  Output:
//  CT = f3473802e38a3ffef4d4fb8e6aa266ebde553a64528a06463e
//  PT = 2f3b9dcfbae729583b1d1ffdd16bb6fe2757329435662a78f0