(Excel) 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.

Download Excel Class Modules Chilkat Excel Class Modules

' 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 Chilkat.CkGlobal
Set chilkatGlob = Chilkat.NewCkGlobal

success = chilkatGlob.UnlockBundle("Anything for 30-day trial.")
If (success <> True) Then
    Debug.Print chilkatGlob.LastErrorText
    Exit Sub
End If

Dim fortuna As Chilkat.Prng
Set fortuna = Chilkat.NewPrng

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


exportedEntropy = 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 Chilkat.Prng
Set fortuna2 = Chilkat.NewPrng
success = fortuna2.ImportEntropy(exportedEntropy)

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