Objective-C

Compress and Encrypt a Large File (Low and Constant Memory Footprint)

See more Compression Examples

Demonstrates how to compress and encrypt a large file such that the memory footprint remains low and constant.

Note: This example requires Chilkat v9.5.0.99 or greater.

Objective-C

#import <CkoCompression.h>
#import <CkoJsonObject.h>
#import <NSString.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.

CkoCompression *compress = [[CkoCompression alloc] init];
compress.Algorithm = @"deflate";

// Set encryption params.
// The possible values are the same as for the corresponding properties in the Chilkat Crypt2 class/object.
// The encoded IV and Key must be specified as hex.
CkoJsonObject *json = [[CkoJsonObject alloc] init];
[json UpdateString: @"cryptAlgorithm" value: @"aes"];
[json UpdateString: @"cipherMode" value: @"cbc"];
[json UpdateInt: @"keyLength" value: [NSNumber numberWithInt: 128]];
[json UpdateInt: @"paddingScheme" value: [NSNumber numberWithInt: 0]];
[json UpdateString: @"encodedIV" value: @"000102030405060708090A0B0C0D0E0F"];
[json UpdateString: @"encodedKey" value: @"000102030405060708090A0B0C0D0E0F"];

// Do file-to-file compression+encryption in a single call.
NSString *inPath = @"qa_data/largeFile.dat";
NSString *outPath = @"c:/temp/qa_output/compressed_encrypted.dat";
success = [compress CompressEncryptFile: json srcPath: inPath destPath: outPath];
if (success == NO) {
    NSLog(@"%@",compress.LastErrorText);
    return;
}

// We can do file-to-file decrypt/decompress like this:
NSString *inPath2 = outPath;
NSString *outPath2 = @"c:/temp/qa_output/restored.dat";
success = [compress DecryptDecompressFile: json srcPath: inPath2 destPath: outPath2];
if (success == NO) {
    NSLog(@"%@",compress.LastErrorText);
    return;
}

// Note: The above decrypt + decompress is the equivalent of doing the same in these two steps:
CkoCrypt2 *crypt = [[CkoCrypt2 alloc] init];
crypt.CryptAlgorithm = @"aes";
crypt.CipherMode = @"cbc";
crypt.KeyLength = [NSNumber numberWithInt:128];
crypt.PaddingScheme = [NSNumber numberWithInt:0];
[crypt SetEncodedIV: @"000102030405060708090A0B0C0D0E0F" encoding: @"hex"];
[crypt SetEncodedKey: @"000102030405060708090A0B0C0D0E0F" encoding: @"hex"];

NSString *decryptedPath = @"c:/temp/qa_output/decrypted.dat";
success = [crypt CkDecryptFile: inPath2 destFile: decryptedPath];
if (success == NO) {
    NSLog(@"%@",crypt.LastErrorText);
    return;
}

NSString *outPath3 = @"c:/temp/qa_output/restored_in_two_steps.dat";
success = [compress DecompressFile: decryptedPath destPath: outPath3];
if (success == NO) {
    NSLog(@"%@",compress.LastErrorText);
    return;
}

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