{ This example signs data using the RSA method from a file to memory in 8K (8192 byte) chunks. }  

uses XceedEncryptionLib_TLB

const CHUNKSIZE = 8192; 

var
  xSign : TXceedSigning; 
  xRSA : DXceedRSASigningMethod; 
  vaBytesRead : OleVariant; 
  vaSignature : OleVariant; 
  vaSeed : OleVariant; 
  lOffset : Longint; 
  lFileSize : Longint; 
  SourceFile : file of byte; 
begin
  xSign := TXceedSigning.Create( self ); 
  xSign.License( 'your license key' ); 

  xRSA := CoXceedRSASigningMethod.Create();  

  try 
    { The following call to SetRandomKeyPair would, in the real world,  
      be replaced by the assignment of a Private Key to the  
      PrivateKey property. }  

    vaSeed := varEmpty; 

    xRSA.SetRandomKeyPair( 512, vaSeed ); 

    xSign.SigningMethod := xRSA;  

    AssignFile( SourceFile, 'c:\temp\source.txt' ); 

    Reset( SourceFile ); 

    lFileSize := FileSize( SourceFile ); 

    CloseFile( SourceFile ); 

    lOffset := 0;  

    while lOffset < lFileSize do 
    begin 
      { bEndOfData will be true if the current offset + CHUNKSIZE exceeds the end of the file. } 
      vaBytesRead := xSign.ReadFile( 'c:\temp\source.txt', lOffset, CHUNKSIZE, efpSign, 
                                     (lOffset + CHUNKSIZE >= lFileSize) ); 

      lOffset := lOffset + vaBytesRead; 
    end;  

    vaSignature := xRSA.Get_Signature;  

    { Do something with the Signature... }  

    ShowMessage( 'Signing successful!' ); 
    lOffset := 0;  

    while lOffset < lFileSize do 
    begin 
      { bEndOfData will be true if the current offset + CHUNKSIZE exceeds the end of the file. } 
      vaBytesRead := xSign.ReadFile( 'c:\temp\source.txt', lOffset, CHUNKSIZE, efpVerify,
                                     (lOffset + CHUNKSIZE >= lFileSize) ); 

      lOffset := lOffset + vaBytesRead; 
    end;  

    ShowMessage( 'Data verified successfully' ); 
  except 
    on xErr : Exception do 
      ShowMessage( xErr.Message ); 
  end;  

  xSign.Free; 
end;