How to decrypt an Excel file

Protect Excel files & cells with a password

Excel files can often contain sensitive data and access must therefore be limited. In addition, there are often situations in which the data should be visible but not manipulated by the end user. We will introduce you to both, but point out that there is no such thing as one hundred percent security with Excel data encryption.

Basically, Excel passwords can be cracked relatively easily, Excel uses a very weak form of encryption. Passwords in older versions of Excel (anything before 2010) are extremely easy to decrypt. If you still have sensitive data in Excel, we recommend using at least a version from Excel 2010.

There are several ways to protect data in Excel.

  1. Protect worksheet (or parts / cells of a worksheet)
  2. Protect workbook
  3. Protect file

Important: Method 1 and 2 only protect certain partial elements and do not prevent unauthorized opening of the file.

1. Protect worksheet (cells)

You start with the "Check" tab. There you will find Protect Sheet and Workbook. For example, if we want to protect the following cells, we use the Protect Sheet option.

In this example from our Excel budget book lesson (download here), we want to protect the cells in the "Overview" area. Users can change the cells in the revenue area below, but the formulas above, which calculate the balance, cannot be manipulated.

In the standard setting, all cells are preset in Excel for protection, i.e. if we now select "Protect sheet", all cells in the example above will be protected. To change that, we select cells in the Income area.

Then either right-click-> Format cells or call up cell formatting with the key combination CTRL + 1.

Then remove the check mark to unlock the selected cells.

The last step is to protect the entire worksheet, the cells that have just been unlocked are then not protected (but the rest of the sheet can no longer be manipulated without a password).

  1. Select Protect Sheet
  2. Choose what users are allowed to do. In the basic setting, users are only allowed to select cells, but not edit them
  3. Enter a password and confirm it a second time in the next window

If you now want to edit a cell in the protected area, this window should appear:

Do you want to lock the entire worksheet instead of just a few cells? This is easy because all cells are set as blocked in the basic setting. Just assign a password to the worksheet as in the previous step and all cells are locked.

Tip: To make sure that all cells are locked, first select all cells via CTRL + A or by clicking on the box at the top left (see screenshot). Then use Format cells to set the protection to "Locked".

2. Protect workbooks structure

Another option is "Protect workbook". Use this if you want to prevent the user from inserting new worksheets, moving, deleting or showing / hiding existing worksheets.

3. Protect Excel file access with a password

Last but not least, in many cases you want to protect the entire file, i.e. when a user opens the Excel file, he must first enter a password (see screenshot).

To set a password, you simply have to enter a password twice when you "Save As" your file. Before you click on “Save”, first set the password under “Tools” and “General Options”.

That was the basics for backing up your Excel files. As I said, it is important to use versions from Excel 2010 onwards and to use strong passwords, otherwise it is too easy to crack them.