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Microsoft Excel supports three levels of workbook file protection. The user who creates a workbook has read/write permission to a workbook and controls the protection level. The three levels of workbook protection are:
Excel requires the user to enter a password to open a workbook.
Excel requires the user to enter a password to open the workbook with read/write permission. The user can click Read Only at the prompt, and Excel opens the workbook read-only.
Excel prompts the user to open the workbook as read-only. If the user clicks No at the prompt, Excel opens the workbook with read/write permission, unless the workbook has other password protection.
Excel encrypts password-protected workbooks by using the symmetric encryption routine known as 40-bit RC4. Because protected workbooks are encrypted, they are not indexed by Find Fast or by the Microsoft Office Server Extensions (OSE) search feature.
Note Strong encryption such as RC4 is banned in France. If a user’s locale setting in Regional Settings in Control Panel is set to French (Standard), that user is not able to open an Office document that is password protected. Nor can the user save an Office document with RC4 encryption. The user can, however, use XOR encryption by saving an Office document with password protection.
In addition to protecting an entire workbook, you can also protect specific elements from unauthorized changes. This method is not as secure as using a password to protect the entire workbook because Excel does not use encryption when you protect only specific elements.
For example, cells that are hidden on a protected worksheet can be viewed if a user copies across a range on the protected worksheet that includes the hidden cells, opens a new workbook, pastes, and then uses the Unhide command to display the cells.
Tip To ensure the strongest security on a workbook, use a password to protect the entire workbook.
The specific elements that you can protect in a workbook include the following:
Worksheets and chart sheets in a protected workbook cannot be moved, deleted, hidden, unhidden, or renamed, and new sheets cannot be inserted.
Windows in a protected workbook cannot be moved, resized, hidden, unhidden, or closed. Windows in a protected workbook are sized and positioned the same way each time the workbook is opened.
Contents of protected cells on a worksheet cannot be edited. Protected items on a chart sheet cannot be modified.
Protected graphic objects cannot be moved or edited.
Protected formulas cannot be edited.
Tip You can also hide a formula so that it does not appear in the formula bar but the formula results appear in the cell.
Definitions of protected scenarios cannot be changed.
Protected change histories cannot be cleared by the user of a shared workbook or by the user of a copy of a workbook that is to be merged.
Caution If a user assigns password protection to a workbook and then forgets the password, you cannot open the workbook, gain access to its data in another workbook through links, remove protection from the workbook, or recover data from the workbook. Advise your users to keep a list of passwords and corresponding workbook, worksheet, and chart sheet names in a safe place.
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