(C) Streaming Encryption

Encrypt and decrypt using a stream.

Chilkat C/C++ Library Downloads
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#include <C_CkCrypt2.h>
#include <C_CkStream.h>
#include <C_CkStringArray.h>
#include <C_CkTask.h>

void ChilkatSample(void)
    {
    HCkCrypt2 crypt;
    const char *ivHex;
    const char *keyHex;
    const char *plainText;
    HCkStream stream;
    HCkStringArray eStrings;
    HCkTask task;
    BOOL success;
    const char *cipherText;
    int i;
    int n;

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

    crypt = CkCrypt2_Create();

    // Setup encryption using the chacha20 algorithm...
    CkCrypt2_putCryptAlgorithm(crypt,"chacha20");
    CkCrypt2_putKeyLength(crypt,256);
    CkCrypt2_putEncodingMode(crypt,"hex");
    ivHex = "000000000000000000000002";
    CkCrypt2_SetEncodedIV(crypt,ivHex,"hex");
    CkCrypt2_putInitialCount(crypt,42);
    keyHex = "1c9240a5eb55d38af333888604f6b5f0473917c1402b80099dca5cbc207075c0";
    CkCrypt2_SetEncodedKey(crypt,keyHex,"hex");

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

    stream = CkStream_Create();

    // We'll save the encrypted output in eStrings to demonstrate streaming decryption next.
    eStrings = CkStringArray_Create();

    // Start a background task that will encrypt a stream.
    task = CkCrypt2_EncryptStreamAsync(crypt,stream);
    success = CkTask_Run(task);

    // Write plainText to the stream, and read chacha20 encrypted text..

    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 = CkStream_WriteString(stream,plainText);
        if (CkStream_getDataAvailable(stream) == TRUE) {
            cipherText = CkStream_readBytesENC(stream,"hex");
            printf("%s\n",cipherText);
            success = CkStringArray_Append(eStrings,cipherText);
        }

    }

    // Tell the background task that the stream has ended.
    success = CkStream_WriteClose(stream);

    // Let's make sure the background task finished.
    // It should already be the case that the task is finished.
    while ((CkTask_getFinished(task) != TRUE)) {
        CkTask_SleepMs(task,20);
    }

    // Get any remaining data available from the stream.
    if (CkStream_getDataAvailable(stream) == TRUE) {
        cipherText = CkStream_readBytesENC(stream,"hex");
        printf("%s\n",cipherText);
        success = CkStringArray_Append(eStrings,cipherText);
    }

    if (CkTask_getTaskSuccess(task) != TRUE) {
        printf("async encryption failed:\n");
        printf("%s\n",CkTask_resultErrorText(task));
        success = FALSE;
    }

    CkTask_Dispose(task);

    printf("-- encrypt finished --\n");

    // Now decrypt to return the original.

    // Reset the stream object so it can be used again.
    CkStream_Reset(stream);

    // Start a background task that will decrypt a stream.
    task = CkCrypt2_DecryptStreamAsync(crypt,stream);
    success = CkTask_Run(task);

    n = CkStringArray_getCount(eStrings);
    for (i = 0; i <= n - 1; i++) {
        success = CkStream_WriteBytesENC(stream,CkStringArray_getString(eStrings,i),"hex");
        if (CkStream_getDataAvailable(stream) == TRUE) {
            plainText = CkStream_readString(stream);
            printf("%s\n",plainText);
        }

    }

    // Tell the background task that the stream has ended.
    success = CkStream_WriteClose(stream);

    // Let's make sure the background task finished.
    // It should already be the case that the task is finished.
    while ((CkTask_getFinished(task) != TRUE)) {
        CkTask_SleepMs(task,20);
    }

    // Get any remaining data available from the stream.
    if (CkStream_getDataAvailable(stream) == TRUE) {
        plainText = CkStream_readString(stream);
        printf("%s\n",plainText);
    }

    if (CkTask_getTaskSuccess(task) != TRUE) {
        printf("async decryption failed:\n");
        printf("%s\n",CkTask_resultErrorText(task));
        success = FALSE;
    }

    CkTask_Dispose(task);

    printf("-- decrypt finished --\n");


    CkCrypt2_Dispose(crypt);
    CkStream_Dispose(stream);
    CkStringArray_Dispose(eStrings);

    }