(Objective-C) AES XTS Mode

Demonstrates the AES-XTS mode of operation.

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

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

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

BOOL success;

// 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