(SQL Server) 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 ActiveX Downloads ActiveX for 32-bit and 64-bit Windows

-- Important: See this note about string length limitations for strings returned by sp_OAMethod calls.
--
CREATE PROCEDURE ChilkatSample
AS
BEGIN
    DECLARE @hr int
    -- Important: Do not use nvarchar(max).  See the warning about using nvarchar(max).
    DECLARE @sTmp0 nvarchar(4000)
    -- All Chilkat classes can be unlocked at once at the beginning of a program
    -- by calling UnlockBundle.  It requires a Bundle unlock code.
    DECLARE @chilkatGlob int
    -- Use "Chilkat_9_5_0.Global" for versions of Chilkat < 10.0.0
    EXEC @hr = sp_OACreate 'Chilkat.Global', @chilkatGlob OUT
    IF @hr <> 0
    BEGIN
        PRINT 'Failed to create ActiveX component'
        RETURN
    END

    DECLARE @success int
    EXEC sp_OAMethod @chilkatGlob, 'UnlockBundle', @success OUT, 'Anything for 30-day trial.'
    IF @success <> 1
      BEGIN
        EXEC sp_OAGetProperty @chilkatGlob, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @chilkatGlob
        RETURN
      END

    DECLARE @fortuna int
    -- Use "Chilkat_9_5_0.Prng" for versions of Chilkat < 10.0.0
    EXEC @hr = sp_OACreate 'Chilkat.Prng', @fortuna OUT

    -- Generate random data and periodically add entropy...
    EXEC sp_OAMethod @fortuna, 'GetEntropy', @sTmp0 OUT, 32, 'hex'
    EXEC sp_OAMethod @fortuna, 'AddEntropy', @success OUT, @sTmp0, 'hex'
    EXEC sp_OAMethod @fortuna, 'GenRandom', @sTmp0 OUT, 16, 'hex'
    PRINT @sTmp0
    EXEC sp_OAMethod @fortuna, 'GenRandom', @sTmp0 OUT, 16, 'hex'
    PRINT @sTmp0
    EXEC sp_OAMethod @fortuna, 'GenRandom', @sTmp0 OUT, 16, 'hex'
    PRINT @sTmp0
    EXEC sp_OAMethod @fortuna, 'GetEntropy', @sTmp0 OUT, 16, 'hex'
    EXEC sp_OAMethod @fortuna, 'AddEntropy', @success OUT, @sTmp0, 'hex'
    EXEC sp_OAMethod @fortuna, 'GenRandom', @sTmp0 OUT, 16, 'hex'
    PRINT @sTmp0
    EXEC sp_OAMethod @fortuna, 'GenRandom', @sTmp0 OUT, 16, 'hex'
    PRINT @sTmp0
    EXEC sp_OAMethod @fortuna, 'GenRandom', @sTmp0 OUT, 16, 'hex'
    PRINT @sTmp0
    EXEC sp_OAMethod @fortuna, 'GetEntropy', @sTmp0 OUT, 16, 'hex'
    EXEC sp_OAMethod @fortuna, 'AddEntropy', @success OUT, @sTmp0, 'hex'
    EXEC sp_OAMethod @fortuna, 'GenRandom', @sTmp0 OUT, 16, 'hex'
    PRINT @sTmp0
    EXEC sp_OAMethod @fortuna, 'GenRandom', @sTmp0 OUT, 16, 'hex'
    PRINT @sTmp0
    EXEC sp_OAMethod @fortuna, 'GenRandom', @sTmp0 OUT, 16, 'hex'
    PRINT @sTmp0
    EXEC sp_OAMethod @fortuna, 'GetEntropy', @sTmp0 OUT, 16, 'hex'
    EXEC sp_OAMethod @fortuna, 'AddEntropy', @success OUT, @sTmp0, 'hex'
    EXEC sp_OAMethod @fortuna, 'GenRandom', @sTmp0 OUT, 16, 'hex'
    PRINT @sTmp0
    EXEC sp_OAMethod @fortuna, 'GenRandom', @sTmp0 OUT, 16, 'hex'
    PRINT @sTmp0
    EXEC sp_OAMethod @fortuna, 'GenRandom', @sTmp0 OUT, 16, 'hex'
    PRINT @sTmp0

    DECLARE @exportedEntropy nvarchar(4000)
    EXEC sp_OAMethod @fortuna, 'ExportEntropy', @exportedEntropy OUT
    -- 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:
    DECLARE @fortuna2 int
    -- Use "Chilkat_9_5_0.Prng" for versions of Chilkat < 10.0.0
    EXEC @hr = sp_OACreate 'Chilkat.Prng', @fortuna2 OUT

    EXEC sp_OAMethod @fortuna2, 'ImportEntropy', @success OUT, @exportedEntropy

    -- Generate more random data, continuing to add entropy as we go along..
    EXEC sp_OAMethod @fortuna2, 'GenRandom', @sTmp0 OUT, 16, 'hex'
    PRINT @sTmp0
    EXEC sp_OAMethod @fortuna2, 'GenRandom', @sTmp0 OUT, 16, 'hex'
    PRINT @sTmp0
    EXEC sp_OAMethod @fortuna2, 'GenRandom', @sTmp0 OUT, 16, 'hex'
    PRINT @sTmp0
    EXEC sp_OAMethod @fortuna2, 'GetEntropy', @sTmp0 OUT, 16, 'hex'
    EXEC sp_OAMethod @fortuna2, 'AddEntropy', @success OUT, @sTmp0, 'hex'
    EXEC sp_OAMethod @fortuna2, 'GenRandom', @sTmp0 OUT, 16, 'hex'
    PRINT @sTmp0
    EXEC sp_OAMethod @fortuna2, 'GenRandom', @sTmp0 OUT, 16, 'hex'
    PRINT @sTmp0
    EXEC sp_OAMethod @fortuna2, 'GenRandom', @sTmp0 OUT, 16, 'hex'
    PRINT @sTmp0
    EXEC sp_OAMethod @fortuna2, 'GetEntropy', @sTmp0 OUT, 16, 'hex'
    EXEC sp_OAMethod @fortuna2, 'AddEntropy', @success OUT, @sTmp0, 'hex'
    -- ..

    EXEC @hr = sp_OADestroy @chilkatGlob
    EXEC @hr = sp_OADestroy @fortuna
    EXEC @hr = sp_OADestroy @fortuna2


END
GO