Objective-C

AES Encrypt and Decrypt a File

_LANGUAGE_ demonstrates how to AES encrypt a file of any size, and then decrypt. Objective-C

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

BOOL success = NO;

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

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

crypt.CryptAlgorithm = @"aes";

//  CipherMode may be "ecb" or "cbc"
crypt.CipherMode = @"cbc";

//  KeyLength may be 128, 192, 256
crypt.KeyLength = [NSNumber numberWithInt:256];

//  The padding scheme determines the contents of the bytes
//  that are added to pad the result to a multiple of the
//  encryption algorithm's block size.  AES has a block
//  size of 16 bytes, so encrypted output is always
//  a multiple of 16.
crypt.PaddingScheme = [NSNumber numberWithInt:0];

//  An initialization vector is required if using CBC mode.
//  ECB mode does not use an IV.
//  The length of the IV is equal to the algorithm's block size.
//  It is NOT equal to the length of the key.
NSString *ivHex = @"000102030405060708090A0B0C0D0E0F";
[crypt SetEncodedIV: ivHex encoding: @"hex"];

//  The secret key must equal the size of the key.  For
//  256-bit encryption, the binary secret key is 32 bytes.
//  For 128-bit encryption, the binary secret key is 16 bytes.
NSString *keyHex = @"000102030405060708090A0B0C0D0E0F101112131415161718191A1B1C1D1E1F";
[crypt SetEncodedKey: keyHex encoding: @"hex"];

//  Encrypt a file, producing the .aes as output.
//  The input file is unchanged, the output .aes contains the encrypted
//  contents of the input file.

//  Note: The .aes output file has no file format.  It is simply a stream
//  of bytes that resembles random binary data.
NSString *inFile = @"/Users/chilkat/testData/pdf/sample.pdf";
NSString *outFile = @"/Users/chilkat/testData/p7m/sample.pdf.aes";
success = [crypt CkEncryptFile: inFile destFile: outFile];
if (success != YES) {
    NSLog(@"%@",crypt.LastErrorText);
    return;
}

//  For demonstration purposes, a different instance of the object will be used
//  for decryption.
CkoCrypt2 *decrypt = [[CkoCrypt2 alloc] init];

//  All settings must match to be able to decrypt:
decrypt.CryptAlgorithm = @"aes";
decrypt.CipherMode = @"cbc";
decrypt.KeyLength = [NSNumber numberWithInt:256];
decrypt.PaddingScheme = [NSNumber numberWithInt:0];
[decrypt SetEncodedIV: ivHex encoding: @"hex"];
[decrypt SetEncodedKey: keyHex encoding: @"hex"];

//  Decrypt the .aes
inFile = @"/Users/chilkat/testData/p7m/sample.pdf.aes";
outFile = @"/Users/chilkat/testData/pdf/recovered.pdf";
success = [decrypt CkDecryptFile: inFile destFile: outFile];
if (success == NO) {
    NSLog(@"%@",decrypt.LastErrorText);
    return;
}

NSLog(@"%@",@"Success!");