(Xojo Plugin) 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 Xojo Plugin Download Xojo Plugin for Windows, Linux, Mac OS X, and ARM, ARM64

// 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.CkGlobal
Dim success As Boolean
success = chilkatGlob.UnlockBundle("Anything for 30-day trial.")
If (success <> True) Then
    System.DebugLog(chilkatGlob.LastErrorText)
    Return
End If

Dim fortuna As New Chilkat.Prng

// Generate random data and periodically add entropy...
success = fortuna.AddEntropy(fortuna.GetEntropy(32,"hex"),"hex")
System.DebugLog(fortuna.GenRandom(16,"hex"))
System.DebugLog(fortuna.GenRandom(16,"hex"))
System.DebugLog(fortuna.GenRandom(16,"hex"))
success = fortuna.AddEntropy(fortuna.GetEntropy(16,"hex"),"hex")
System.DebugLog(fortuna.GenRandom(16,"hex"))
System.DebugLog(fortuna.GenRandom(16,"hex"))
System.DebugLog(fortuna.GenRandom(16,"hex"))
success = fortuna.AddEntropy(fortuna.GetEntropy(16,"hex"),"hex")
System.DebugLog(fortuna.GenRandom(16,"hex"))
System.DebugLog(fortuna.GenRandom(16,"hex"))
System.DebugLog(fortuna.GenRandom(16,"hex"))
success = fortuna.AddEntropy(fortuna.GetEntropy(16,"hex"),"hex")
System.DebugLog(fortuna.GenRandom(16,"hex"))
System.DebugLog(fortuna.GenRandom(16,"hex"))
System.DebugLog(fortuna.GenRandom(16,"hex"))

Dim exportedEntropy As String
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 New Chilkat.Prng
success = fortuna2.ImportEntropy(exportedEntropy)

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