(MFC) Streaming Encryption

Encrypt and decrypt using a stream.

Chilkat C/C++ Library Downloads MS Visual C/C++ Libs

See Also: Using MFC CString in Chilkat

#include <CkCrypt2.h>
#include <CkStream.h>
#include <CkStringArray.h>
#include <CkTask.h>

void ChilkatSample(void)
    {
    CkString strOut;

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

    CkCrypt2 crypt;

    // Setup encryption using the chacha20 algorithm...
    crypt.put_CryptAlgorithm("chacha20");
    crypt.put_KeyLength(256);
    crypt.put_EncodingMode("hex");
    const char *ivHex = "000000000000000000000002";
    crypt.SetEncodedIV(ivHex,"hex");
    crypt.put_InitialCount(42);
    const char *keyHex = "1c9240a5eb55d38af333888604f6b5f0473917c1402b80099dca5cbc207075c0";
    crypt.SetEncodedKey(keyHex,"hex");

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

    CkStream stream;

    // We'll save the encrypted output in eStrings to demonstrate streaming decryption next.
    CkStringArray eStrings;

    // Start a background task that will encrypt a stream.
    CkTask *task = crypt.EncryptStreamAsync(stream);
    bool success = task->Run();

    // Write plainText to the stream, and read chacha20 encrypted text..
    const char *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.get_DataAvailable() == true) {
            cipherText = stream.readBytesENC("hex");
            strOut.append(cipherText);
            strOut.append("\r\n");
            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->get_Finished() != true)) {
        task->SleepMs(20);
    }

    // Get any remaining data available from the stream.
    if (stream.get_DataAvailable() == true) {
        cipherText = stream.readBytesENC("hex");
        strOut.append(cipherText);
        strOut.append("\r\n");
        success = eStrings.Append(cipherText);
    }

    if (task->get_TaskSuccess() != true) {
        strOut.append("async encryption failed:");
        strOut.append("\r\n");
        strOut.append(task->resultErrorText());
        strOut.append("\r\n");
        success = false;
    }

    delete task;

    strOut.append("-- encrypt finished --");
    strOut.append("\r\n");

    // 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.get_Count();
    for (i = 0; i <= n - 1; i++) {
        success = stream.WriteBytesENC(eStrings.getString(i),"hex");
        if (stream.get_DataAvailable() == true) {
            plainText = stream.readString();
            strOut.append(plainText);
            strOut.append("\r\n");
        }

    }

    // 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->get_Finished() != true)) {
        task->SleepMs(20);
    }

    // Get any remaining data available from the stream.
    if (stream.get_DataAvailable() == true) {
        plainText = stream.readString();
        strOut.append(plainText);
        strOut.append("\r\n");
    }

    if (task->get_TaskSuccess() != true) {
        strOut.append("async decryption failed:");
        strOut.append("\r\n");
        strOut.append(task->resultErrorText());
        strOut.append("\r\n");
        success = false;
    }

    delete task;

    strOut.append("-- decrypt finished --");
    strOut.append("\r\n");


    SetDlgItemText(IDC_EDIT1,strOut.getUnicode());

    }