(PureBasic) Streaming Encryption

Encrypt and decrypt using a stream.

Chilkat PureBasic Module Download Chilkat PureBasic Module

IncludeFile "CkTask.pb"
IncludeFile "CkStream.pb"
IncludeFile "CkStringArray.pb"
IncludeFile "CkCrypt2.pb"

Procedure ChilkatExample()

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

    crypt.i = CkCrypt2::ckCreate()
    If crypt.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    ; Setup encryption using the chacha20 algorithm...
    CkCrypt2::setCkCryptAlgorithm(crypt, "chacha20")
    CkCrypt2::setCkKeyLength(crypt, 256)
    CkCrypt2::setCkEncodingMode(crypt, "hex")
    ivHex.s = "000000000000000000000002"
    CkCrypt2::ckSetEncodedIV(crypt,ivHex,"hex")
    CkCrypt2::setCkInitialCount(crypt, 42)
    keyHex.s = "1c9240a5eb55d38af333888604f6b5f0473917c1402b80099dca5cbc207075c0"
    CkCrypt2::ckSetEncodedKey(crypt,keyHex,"hex")

    plainText.s = "The quick brown fox jumped over the lazy dog." + Chr(13) + Chr(10)

    stream.i = CkStream::ckCreate()
    If stream.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    ; We'll save the encrypted output in eStrings to demonstrate streaming decryption next.
    eStrings.i = CkStringArray::ckCreate()
    If eStrings.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    ; Start a background task that will encrypt a stream.
    task.i = CkCrypt2::ckEncryptStreamAsync(crypt,stream)
    success.i = CkTask::ckRun(task)

    ; Write plainText to the stream, and read chacha20 encrypted text..
    cipherText.s
    i.i
    For i = 1 To 10
        ; Note: An encryption algorithm's block size will cause buffering,
        ; and therefore not every loop iteration will produce output.
        success = CkStream::ckWriteString(stream,plainText)
        If CkStream::ckDataAvailable(stream) = 1
            cipherText = CkStream::ckReadBytesENC(stream,"hex")
            Debug cipherText
            success = CkStringArray::ckAppend(eStrings,cipherText)
        EndIf

    Next

    ; Tell the background task that the stream has ended.
    success = CkStream::ckWriteClose(stream)

    ; Let's make sure the background task finished.
    ; It should already be the case that the task is finished.
    While (CkTask::ckFinished(task) <> 1)
        CkTask::ckSleepMs(task,20)
    Wend

    ; Get any remaining data available from the stream.
    If CkStream::ckDataAvailable(stream) = 1
        cipherText = CkStream::ckReadBytesENC(stream,"hex")
        Debug cipherText
        success = CkStringArray::ckAppend(eStrings,cipherText)
    EndIf

    If CkTask::ckTaskSuccess(task) <> 1
        Debug "async encryption failed:"
        Debug CkTask::ckResultErrorText(task)
        success = 0
    EndIf

    CkTask::ckDispose(task)

    Debug "-- encrypt finished --"

    ; Now decrypt to return the original.

    ; Reset the stream object so it can be used again.
    CkStream::ckReset(stream)

    ; Start a background task that will decrypt a stream.
    task = CkCrypt2::ckDecryptStreamAsync(crypt,stream)
    success = CkTask::ckRun(task)

    n.i = CkStringArray::ckCount(eStrings)
    For i = 0 To n - 1
        success = CkStream::ckWriteBytesENC(stream,CkStringArray::ckGetString(eStrings,i),"hex")
        If CkStream::ckDataAvailable(stream) = 1
            plainText = CkStream::ckReadString(stream)
            Debug plainText
        EndIf

    Next

    ; Tell the background task that the stream has ended.
    success = CkStream::ckWriteClose(stream)

    ; Let's make sure the background task finished.
    ; It should already be the case that the task is finished.
    While (CkTask::ckFinished(task) <> 1)
        CkTask::ckSleepMs(task,20)
    Wend

    ; Get any remaining data available from the stream.
    If CkStream::ckDataAvailable(stream) = 1
        plainText = CkStream::ckReadString(stream)
        Debug plainText
    EndIf

    If CkTask::ckTaskSuccess(task) <> 1
        Debug "async decryption failed:"
        Debug CkTask::ckResultErrorText(task)
        success = 0
    EndIf

    CkTask::ckDispose(task)

    Debug "-- decrypt finished --"


    CkCrypt2::ckDispose(crypt)
    CkStream::ckDispose(stream)
    CkStringArray::ckDispose(eStrings)


    ProcedureReturn
EndProcedure