VB.NET

Compress and Encrypt a Large File (Low and Constant Memory Footprint)

See more Compression Examples

Demonstrates how to compress and encrypt a large file such that the memory footprint remains low and constant.

Note: This example requires Chilkat v9.5.0.99 or greater.

VB.NET

Dim success As Boolean = False

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

Dim compress As New Chilkat.Compression
compress.Algorithm = "deflate"

' Set encryption params.
' The possible values are the same as for the corresponding properties in the Chilkat Crypt2 class/object.
' The encoded IV and Key must be specified as hex.
Dim json As New Chilkat.JsonObject
json.UpdateString("cryptAlgorithm","aes")
json.UpdateString("cipherMode","cbc")
json.UpdateInt("keyLength",128)
json.UpdateInt("paddingScheme",0)
json.UpdateString("encodedIV","000102030405060708090A0B0C0D0E0F")
json.UpdateString("encodedKey","000102030405060708090A0B0C0D0E0F")

' Do file-to-file compression+encryption in a single call.
Dim inPath As String = "qa_data/largeFile.dat"
Dim outPath As String = "c:/temp/qa_output/compressed_encrypted.dat"
success = compress.CompressEncryptFile(json,inPath,outPath)
If (success = False) Then
    Debug.WriteLine(compress.LastErrorText)
    Exit Sub
End If


' We can do file-to-file decrypt/decompress like this:
Dim inPath2 As String = outPath
Dim outPath2 As String = "c:/temp/qa_output/restored.dat"
success = compress.DecryptDecompressFile(json,inPath2,outPath2)
If (success = False) Then
    Debug.WriteLine(compress.LastErrorText)
    Exit Sub
End If


' Note: The above decrypt + decompress is the equivalent of doing the same in these two steps:
Dim crypt As New Chilkat.Crypt2
crypt.CryptAlgorithm = "aes"
crypt.CipherMode = "cbc"
crypt.KeyLength = 128
crypt.PaddingScheme = 0
crypt.SetEncodedIV("000102030405060708090A0B0C0D0E0F","hex")
crypt.SetEncodedKey("000102030405060708090A0B0C0D0E0F","hex")

Dim decryptedPath As String = "c:/temp/qa_output/decrypted.dat"
success = crypt.CkDecryptFile(inPath2,decryptedPath)
If (success = False) Then
    Debug.WriteLine(crypt.LastErrorText)
    Exit Sub
End If


Dim outPath3 As String = "c:/temp/qa_output/restored_in_two_steps.dat"
success = compress.DecompressFile(decryptedPath,outPath3)
If (success = False) Then
    Debug.WriteLine(compress.LastErrorText)
    Exit Sub
End If


Debug.WriteLine("Success.")