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I'd like to encrypt a document securely with MS Word. As far as I know the default encryption algorithm is not secure ("Office 97/2000 Compatible"), and neither XOR encryption. However, there are numerous other to choose from, but i am not sure of the differences. There are "base", "enhanced" and "strong" varieties, but other options too. So which to select, for regular passphrase encryption?

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I found this document with some details, but it was not of much help:

Note: this is MS Word 2003, it looks like there are no options for different algorithms in Office 2007, presumably the 2007 defaults are more secure than the 2003 defaults. However, if saving a document in Word 2007 as a 97/2000 compatible document (.doc), which encryption algorithm is selected?

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up vote 0 down vote accepted

The different types of encryption are explained here:
Changes in encryption file properties in Office 2003 and Office 2002
under the section "Encryption Types That You May See Listed in Office".

If you're concerned about security, just use the strongest that your Word version supports (some geographical considerations may apply).

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Encryption was basic in Word until the introduction in Word 97 of a proprietary technique (maintained in Word 2000) that was effective at the time. If you wanted to put a password on a document in Word 2000 this is where you would do it, in a dialog that hadn't significantly changed since I don't know when:

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There isn't much to be said about this. One told Word to put a password on a document, and Word did so, encrypting the contents using its own process.

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