(Lianja) Streaming Encryption

Encrypt and decrypt using a stream.

Chilkat Lianja Extension Download Chilkat Lianja Extension

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

loCrypt = createobject("CkCrypt2")

// Setup encryption using the chacha20 algorithm...
loCrypt.CryptAlgorithm = "chacha20"
loCrypt.KeyLength = 256
loCrypt.EncodingMode = "hex"
lcIvHex = "000000000000000000000002"
loCrypt.SetEncodedIV(lcIvHex,"hex")
loCrypt.InitialCount = 42
lcKeyHex = "1c9240a5eb55d38af333888604f6b5f0473917c1402b80099dca5cbc207075c0"
loCrypt.SetEncodedKey(lcKeyHex,"hex")

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

loStream = createobject("CkStream")

// We'll save the encrypted output in eStrings to demonstrate streaming decryption next.
loEStrings = createobject("CkStringArray")

// Start a background task that will encrypt a stream.
loTask = loCrypt.EncryptStreamAsync(loStream)
llSuccess = loTask.Run()

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

for i = 1 to 10
    // Note: An encryption algorithm's block size will cause buffering,
    // and therefore not every loop iteration will produce output.
    llSuccess = loStream.WriteString(lcPlainText)
    if (loStream.DataAvailable = .T.) then
        lcCipherText = loStream.ReadBytesENC("hex")
        ? lcCipherText
        llSuccess = loEStrings.Append(lcCipherText)
    endif

next

// Tell the background task that the stream has ended.
llSuccess = loStream.WriteClose()

// Let's make sure the background task finished.
// It should already be the case that the task is finished.
do while (loTask.Finished <> .T.)
    loTask.SleepMs(20)
enddo

// Get any remaining data available from the stream.
if (loStream.DataAvailable = .T.) then
    lcCipherText = loStream.ReadBytesENC("hex")
    ? lcCipherText
    llSuccess = loEStrings.Append(lcCipherText)
endif

if (loTask.TaskSuccess <> .T.) then
    ? "async encryption failed:"
    ? loTask.ResultErrorText
    llSuccess = .F.
endif

release loTask

? "-- encrypt finished --"

// Now decrypt to return the original.

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

// Start a background task that will decrypt a stream.
loTask = loCrypt.DecryptStreamAsync(loStream)
llSuccess = loTask.Run()

n = loEStrings.Count
for i = 0 to n - 1
    llSuccess = loStream.WriteBytesENC(loEStrings.GetString(i),"hex")
    if (loStream.DataAvailable = .T.) then
        lcPlainText = loStream.ReadString()
        ? lcPlainText
    endif

next

// Tell the background task that the stream has ended.
llSuccess = loStream.WriteClose()

// Let's make sure the background task finished.
// It should already be the case that the task is finished.
do while (loTask.Finished <> .T.)
    loTask.SleepMs(20)
enddo

// Get any remaining data available from the stream.
if (loStream.DataAvailable = .T.) then
    lcPlainText = loStream.ReadString()
    ? lcPlainText
endif

if (loTask.TaskSuccess <> .T.) then
    ? "async decryption failed:"
    ? loTask.ResultErrorText
    llSuccess = .F.
endif

release loTask

? "-- decrypt finished --"


release loCrypt
release loStream
release loEStrings