AFAIK both Microsoft Office and LibreOffice have features to add passwords to protect the content.

In general, there are two ways:

  • protect from editing/changing (without a revision at least)
  • protect from opening (without password)

Now I've looked at some old LibreOffice questions and some Stackexchange questions and even found this nice Wikipedia article about the MS Office password protection.

However, all of them mostly just seem to tackle the encryption when saving, i.e. the password to open a document.

However, there is no general overview and especially no evaluation on the security of the "editing lock" passwords.

Thus, how secure are both of these?

  • The general advice would be twofold: (1). "protect from editing local file" is a useless feature: anyone who can read the file can copy the contents and then modify the copy. On data stored in some kind of remote/cloud storage, protection from modification makes total sense. (2). Don't use cryptography features (e.g. encryption or digital signatures) of non-security software. Any tool that is not a dedicated tool only for encryption/signatures. Web servers that do TLS kind of violate this, but in general, good rule. I would use something like jedisct1's minisign & encpipe. – Z.T. May 25 at 20:58

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