Encryption & Security

Encryption

  • Do you want to securely encrypt data in or outside of your spreadsheet?
  • How would you like to use the best encryption available, say one of the finalists in the selection for the US encryption standards?
  • Would you like to be able to use public key encryption without having to install PGP, or would you like to digitally sign documents?
  • Would you like a pure VBA solution, which does not involve any additional DLL's or OCX's?
  • Would you like to protect proprietary data by "signing" it?

    If you answered yes to any of these, I may have something for you...

    Adding a digital signature to an Excel workbook

    Excel XP offers a digital signature facility, but it's not much use to anyone with a certified digital signature. This file shows what I think is a much better way to do this.

    Getting a "hash" value for a file

    SHA256 is a well known algorithm for calculating a short string based on the contents of a file, which is effectively unique. It would be extremely difficult to alter the file and obtain the same hash. Find out how to do it here.

    How secure is Excel?

    I've written down everything I know about Excel security in an article here.

    "Signing" proprietary data

    Steganography is the art of hiding data in plain sight. This workbook shows how you can embed a message in the less significant digits of your data and no-one will even know it is there. Try it here.

    Microsoft's CryptoAPI

    Microsoft provides an encryption library called the CryptoAPI which is built into most Windows installations. Here's how to use it. It's not the strongest or fastest algorithm around but will serve most purposes.

    Data encryption ( & PIN numbers & pure VBA encryption)

    Some time ago I needed to include individual member data in a spreadsheet to be distributed to all these members. The data had to be REALLY secure. A kind person provided a VBA version (no DLL's or OCX required!) of Blowfish, a world class encryption algorithm, and I wrote code to generate unique PIN numbers and log members in with their date of birth and PIN.

    Security should be strong not only because of Blowfish but because each line of data is encoded with that individual's PIN number, ie guessing a PIN number would only get you one line of data, not all the data. Get it here

    Why not hide the data in a hidden sheet? See what I wrote about Excel security above. It may frighten you.

    		•