(Visual Basic 6.0) Streaming Encryption

Encrypt and decrypt using a stream.

Chilkat ActiveX Downloads ActiveX for 32-bit and 64-bit Windows

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

Dim crypt As New ChilkatCrypt2

' Setup encryption using the chacha20 algorithm...
crypt.CryptAlgorithm = "chacha20"
crypt.KeyLength = 256
crypt.EncodingMode = "hex"
Dim ivHex As String
ivHex = "000000000000000000000002"
crypt.SetEncodedIV ivHex,"hex"
crypt.InitialCount = 42
Dim keyHex As String
keyHex = "1c9240a5eb55d38af333888604f6b5f0473917c1402b80099dca5cbc207075c0"
crypt.SetEncodedKey keyHex,"hex"

Dim plainText As String
plainText = "The quick brown fox jumped over the lazy dog." & vbCrLf

Dim stream As New ChilkatStream

' We'll save the encrypted output in eStrings to demonstrate streaming decryption next.
Dim eStrings As New CkStringArray

' Start a background task that will encrypt a stream.
Dim task As ChilkatTask
Set task = crypt.EncryptStreamAsync(stream)
Dim success As Long
success = task.Run()

' Write plainText to the stream, and read chacha20 encrypted text..
Dim cipherText As String
Dim i As Long
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 = stream.WriteString(plainText)
    If (stream.DataAvailable = 1) Then
        cipherText = stream.ReadBytesENC("hex")
        Debug.Print cipherText
        success = eStrings.Append(cipherText)
    End If

Next

' 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.
Do While (task.Finished <> 1)
    task.SleepMs 20
Loop

' Get any remaining data available from the stream.
If (stream.DataAvailable = 1) Then
    cipherText = stream.ReadBytesENC("hex")
    Debug.Print cipherText
    success = eStrings.Append(cipherText)
End If

If (task.TaskSuccess <> 1) Then
    Debug.Print "async encryption failed:"
    Debug.Print task.ResultErrorText
    success = 0
End If

Debug.Print "-- 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.
Set task = crypt.DecryptStreamAsync(stream)
success = task.Run()

Dim n As Long
n = eStrings.Count
For i = 0 To n - 1
    success = stream.WriteBytesENC(eStrings.GetString(i),"hex")
    If (stream.DataAvailable = 1) Then
        plainText = stream.ReadString()
        Debug.Print plainText
    End If

Next

' 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.
Do While (task.Finished <> 1)
    task.SleepMs 20
Loop

' Get any remaining data available from the stream.
If (stream.DataAvailable = 1) Then
    plainText = stream.ReadString()
    Debug.Print plainText
End If

If (task.TaskSuccess <> 1) Then
    Debug.Print "async decryption failed:"
    Debug.Print task.ResultErrorText
    success = 0
End If

Debug.Print "-- decrypt finished --"