(Objective-C) Streaming Encryption

Encrypt and decrypt using a stream.

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#import <CkoCrypt2.h>
#import <NSString.h>
#import <CkoStream.h>
#import <CkoStringArray.h>
#import <CkoTask.h>

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

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

// Setup encryption using the chacha20 algorithm...
crypt.CryptAlgorithm = @"chacha20";
crypt.KeyLength = [NSNumber numberWithInt:256];
crypt.EncodingMode = @"hex";
NSString *ivHex = @"000000000000000000000002";
[crypt SetEncodedIV: ivHex encoding: @"hex"];
crypt.InitialCount = [NSNumber numberWithInt:42];
NSString *keyHex = @"1c9240a5eb55d38af333888604f6b5f0473917c1402b80099dca5cbc207075c0";
[crypt SetEncodedKey: keyHex encoding: @"hex"];

NSString *plainText = @"The quick brown fox jumped over the lazy dog.\r\n";

CkoStream *stream = [[CkoStream alloc] init];

// We'll save the encrypted output in eStrings to demonstrate streaming decryption next.
CkoStringArray *eStrings = [[CkoStringArray alloc] init];

// Start a background task that will encrypt a stream.
CkoTask *task = [crypt EncryptStreamAsync: stream];
BOOL success = [task Run];

// Write plainText to the stream, and read chacha20 encrypted text..
NSString *cipherText = 0;
int i;
for (i = 1; i <= 10; i++) {
    // Note: An encryption algorithm's block size will cause buffering,
    // and therefore not every loop iteration will produce output.
    success = [stream WriteString: plainText];
    if (stream.DataAvailable == YES) {
        cipherText = [stream ReadBytesENC: @"hex"];
        NSLog(@"%@",cipherText);
        success = [eStrings Append: cipherText];
    }

}

// Tell the background task that the stream has ended.
success = [stream WriteClose];

// Let's make sure the background task finished.
// It should already be the case that the task is finished.
while ((task.Finished != YES)) {
    [task SleepMs: [NSNumber numberWithInt: 20]];
}

// Get any remaining data available from the stream.
if (stream.DataAvailable == YES) {
    cipherText = [stream ReadBytesENC: @"hex"];
    NSLog(@"%@",cipherText);
    success = [eStrings Append: cipherText];
}

if (task.TaskSuccess != YES) {
    NSLog(@"%@",@"async encryption failed:");
    NSLog(@"%@",task.ResultErrorText);
    success = NO;
}

NSLog(@"%@",@"-- encrypt finished --");

// Now decrypt to return the original.

// Reset the stream object so it can be used again.
[stream Reset];

// Start a background task that will decrypt a stream.
task = [crypt DecryptStreamAsync: stream];
success = [task Run];

int n = [eStrings.Count intValue];
for (i = 0; i <= n - 1; i++) {
    success = [stream WriteBytesENC: [eStrings GetString: [NSNumber numberWithInt: i]] encoding: @"hex"];
    if (stream.DataAvailable == YES) {
        plainText = [stream ReadString];
        NSLog(@"%@",plainText);
    }

}

// Tell the background task that the stream has ended.
success = [stream WriteClose];

// Let's make sure the background task finished.
// It should already be the case that the task is finished.
while ((task.Finished != YES)) {
    [task SleepMs: [NSNumber numberWithInt: 20]];
}

// Get any remaining data available from the stream.
if (stream.DataAvailable == YES) {
    plainText = [stream ReadString];
    NSLog(@"%@",plainText);
}

if (task.TaskSuccess != YES) {
    NSLog(@"%@",@"async decryption failed:");
    NSLog(@"%@",task.ResultErrorText);
    success = NO;
}

NSLog(@"%@",@"-- decrypt finished --");