DataFlex

Exporting and Importing Accumulated Entropy

See more PRNG Examples

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.

DataFlex

Use ChilkatAx-win32.pkg

Procedure Test
    Boolean iSuccess
    Handle hoFortuna
    String sExportedEntropy
    Handle hoFortuna2
    String sTemp1

    Move False To iSuccess

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

    Move False To iSuccess

    Get Create (RefClass(cComChilkatPrng)) To hoFortuna
    If (Not(IsComObjectCreated(hoFortuna))) Begin
        Send CreateComObject of hoFortuna
    End

    // Generate random data and periodically add entropy...
    Get ComGetEntropy Of hoFortuna 32 "hex" To sTemp1
    Get ComAddEntropy Of hoFortuna sTemp1 "hex" To iSuccess
    Get ComGenRandom Of hoFortuna 16 "hex" To sTemp1
    Showln sTemp1
    Get ComGenRandom Of hoFortuna 16 "hex" To sTemp1
    Showln sTemp1
    Get ComGenRandom Of hoFortuna 16 "hex" To sTemp1
    Showln sTemp1
    Get ComGetEntropy Of hoFortuna 16 "hex" To sTemp1
    Get ComAddEntropy Of hoFortuna sTemp1 "hex" To iSuccess
    Get ComGenRandom Of hoFortuna 16 "hex" To sTemp1
    Showln sTemp1
    Get ComGenRandom Of hoFortuna 16 "hex" To sTemp1
    Showln sTemp1
    Get ComGenRandom Of hoFortuna 16 "hex" To sTemp1
    Showln sTemp1
    Get ComGetEntropy Of hoFortuna 16 "hex" To sTemp1
    Get ComAddEntropy Of hoFortuna sTemp1 "hex" To iSuccess
    Get ComGenRandom Of hoFortuna 16 "hex" To sTemp1
    Showln sTemp1
    Get ComGenRandom Of hoFortuna 16 "hex" To sTemp1
    Showln sTemp1
    Get ComGenRandom Of hoFortuna 16 "hex" To sTemp1
    Showln sTemp1
    Get ComGetEntropy Of hoFortuna 16 "hex" To sTemp1
    Get ComAddEntropy Of hoFortuna sTemp1 "hex" To iSuccess
    Get ComGenRandom Of hoFortuna 16 "hex" To sTemp1
    Showln sTemp1
    Get ComGenRandom Of hoFortuna 16 "hex" To sTemp1
    Showln sTemp1
    Get ComGenRandom Of hoFortuna 16 "hex" To sTemp1
    Showln sTemp1

    Get ComExportEntropy Of hoFortuna To sExportedEntropy
    // 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:
    Get Create (RefClass(cComChilkatPrng)) To hoFortuna2
    If (Not(IsComObjectCreated(hoFortuna2))) Begin
        Send CreateComObject of hoFortuna2
    End
    Get ComImportEntropy Of hoFortuna2 sExportedEntropy To iSuccess

    // Generate more random data, continuing to add entropy as we go along..
    Get ComGenRandom Of hoFortuna2 16 "hex" To sTemp1
    Showln sTemp1
    Get ComGenRandom Of hoFortuna2 16 "hex" To sTemp1
    Showln sTemp1
    Get ComGenRandom Of hoFortuna2 16 "hex" To sTemp1
    Showln sTemp1
    Get ComGetEntropy Of hoFortuna2 16 "hex" To sTemp1
    Get ComAddEntropy Of hoFortuna2 sTemp1 "hex" To iSuccess
    Get ComGenRandom Of hoFortuna2 16 "hex" To sTemp1
    Showln sTemp1
    Get ComGenRandom Of hoFortuna2 16 "hex" To sTemp1
    Showln sTemp1
    Get ComGenRandom Of hoFortuna2 16 "hex" To sTemp1
    Showln sTemp1
    Get ComGetEntropy Of hoFortuna2 16 "hex" To sTemp1
    Get ComAddEntropy Of hoFortuna2 sTemp1 "hex" To iSuccess
    // ..


End_Procedure