INTELLECTUAL PROPERTY OFFICE OF NEW ZEALAND
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Patent 552724
Patent 552724
A security system to prepare dependent software adapted and secured for use with
independent spreadsheet software is disclosed. The independent spreadsheet software
comprises a means for producing a workbook comprising one or more worksheets. The one
or more worksheets comprise one or more cells and are capable of holding functions,
formulas, computer-executable instructions, sets of instructions, or constants; and the cells
are also capable of holding a user's data or results.
The security system comprises a security means for preventing viewing of formulas, or use
of the workbook by an unauthorised user. The security means comprises a non-distributed
encoder module and the non-distributed encoder module converts the workbook into a
secured form before distribution. Such secured form includes the addition of certain security
conditions, thereby producing a secured workbook with secured content; and the secured
workbook includes in-situ replacement of formulae, excluding user’s data or results, of at
least one selected cell of the secured dependent software with a function whose parameters
contain strongly encrypted ciphertext or a link whereby strongly encrypted ciphertext can be
retrieved.
The security system also comprises a decoder module that is supplied with the workbook.
The decoder module is capable, when in use and only if all predetermined security
conditions are satisfied, of co-operating with the independent spreadsheet software by
detecting a call made by the independent spreadsheet software to a modified addressed cell
within the secured workbook; acquiring, then decoding, the ciphertext and returning a
plaintext version thereof to the independent spreadsheet software and ensuring that access
to the plaintext version by the user is effectively prevented; thereby providing security for the
secured workbook in a persistent form; and thereby keeping the secured content secret from
the user, and preventing the user from viewing, altering, or copying the plaintext contents of
the secured workbook.