(VB.NET UWP/WinRT) Exporting and Importing Accumulated Entropy

When a system starts, a good established source of entropy may be lacking. The Fortuna algorithm keeps 32 internal entropy pools. When AddEntropy is called, it is added to these internal pools. (The details of the Fortuna algorithm can be read elsewhere.)

This example demonstrates how the entropy that has accumulated within the internal pools can be exported (such as when an application exits) and then imported when an application starts. (It is the application's job to persist the exported entropy to a database, file, etc.)

Importing entropy helps ensure an application is beginning with an adequate source of entropy for random number generation.

Chilkat Universal Windows Platform (UWP) / WinRT Downloads Chilkat for the Universal Windows Platform (UWP)

' All Chilkat classes can be unlocked at once at the beginning of a program
' by calling UnlockBundle.  It requires a Bundle unlock code.
Dim chilkatGlob As New Chilkat.Global
Dim success As Boolean = chilkatGlob.UnlockBundle("Anything for 30-day trial.")
If (success <> True) Then
    Debug.WriteLine(chilkatGlob.LastErrorText)
    Exit Sub
End If


Dim fortuna As New Chilkat.Prng

' Generate random data and periodically add entropy...
success = fortuna.AddEntropy(fortuna.GetEntropy(32,"hex"),"hex")
Debug.WriteLine(fortuna.GenRandom(16,"hex"))
Debug.WriteLine(fortuna.GenRandom(16,"hex"))
Debug.WriteLine(fortuna.GenRandom(16,"hex"))
success = fortuna.AddEntropy(fortuna.GetEntropy(16,"hex"),"hex")
Debug.WriteLine(fortuna.GenRandom(16,"hex"))
Debug.WriteLine(fortuna.GenRandom(16,"hex"))
Debug.WriteLine(fortuna.GenRandom(16,"hex"))
success = fortuna.AddEntropy(fortuna.GetEntropy(16,"hex"),"hex")
Debug.WriteLine(fortuna.GenRandom(16,"hex"))
Debug.WriteLine(fortuna.GenRandom(16,"hex"))
Debug.WriteLine(fortuna.GenRandom(16,"hex"))
success = fortuna.AddEntropy(fortuna.GetEntropy(16,"hex"),"hex")
Debug.WriteLine(fortuna.GenRandom(16,"hex"))
Debug.WriteLine(fortuna.GenRandom(16,"hex"))
Debug.WriteLine(fortuna.GenRandom(16,"hex"))

Dim exportedEntropy As String = fortuna.ExportEntropy()
' The application would persist the exported entropy in some way,
' such as to a file, or to a database, etc.

' Create a new PRNG object and initialize the internal entropy pools
' with the previously exported entropy:
Dim fortuna2 As New Chilkat.Prng
success = fortuna2.ImportEntropy(exportedEntropy)

' Generate more random data, continuing to add entropy as we go along..
Debug.WriteLine(fortuna2.GenRandom(16,"hex"))
Debug.WriteLine(fortuna2.GenRandom(16,"hex"))
Debug.WriteLine(fortuna2.GenRandom(16,"hex"))
success = fortuna2.AddEntropy(fortuna2.GetEntropy(16,"hex"),"hex")
Debug.WriteLine(fortuna2.GenRandom(16,"hex"))
Debug.WriteLine(fortuna2.GenRandom(16,"hex"))
Debug.WriteLine(fortuna2.GenRandom(16,"hex"))
success = fortuna2.AddEntropy(fortuna2.GetEntropy(16,"hex"),"hex")
' ..