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PREVIOUS RESEARCH: I have searched for password rulesets/schemes and password sharing, but the articles I have found deal with an individual’s passwords, not a group or team’s passwords.

SCENARIO: I am part of a small work team of about 3 to 4 people. We have sensitive material that occasionally needs to be emailed as an attachment (typically Word documents or PDFs).

I would like to create a password ruleset/scheme for our team that would be applied to the documents that we send. This ruleset should:

  • Easily understood (not too complicated/difficult to create the password)
  • Password is not easily guessed
  • Password is distinct for each document we send
  • Easy for each of the team members to figure out (i.e. a team member can guess another team member's document's password)

The last point deserves some more explanation. It would be highly beneficial if the ruleset/scheme allowed for each of the team members to be able to figure out what the password on the document was, even if s/he did not create the password. My idea was to create a password by combining the senders first name, the recipients last name, and the date.

EXAMPLE: If a team member, Bob, needs to send a document to Jim on December 7, 2017, then the password for the file would be “JimBob1272017”. Likewise, if team member Jack needs to send a document to Jill on February 23, 2018, then the password would be “JackJill2232018”. As long as the other team members know the sender, recipient, and date, then they should be able to figure out the password. Thus, if any team member is ill or resigns, then documents are still accessible.

QUESTIONS: Does anyone have suggestions for creating a password ruleset/scheme that meets the four previously mentioned criteria? Or, can someone provide suggestions to improve the process I’ve described?

NOTES: We do keep track of our passwords, but I was thinking this could be helpful if someone forgot to keep track of a password or if a client forgot the document’s password (and the password creator wasn’t available and the password wasn’t recorded properly).

I don’t think it would be wise to make the team repeatedly use one password for every document (e.g. The team uses “password” for each document’s password), nor would it be wise for each team member to use his/her own personal password repeatedly (e.g. Bob uses “password” for all of his documents, but Jack uses “Acme” for all of his documents).

Thanks!

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    Have you considered using a Password Manager such as KeyPass or Dashlane to share passwords? This way you can use "strong" passwords (IE random 16 character alpha-numeric), and team-members don't have to do any guessing. – Cowthulhu Dec 7 '17 at 18:41
  • Lastpass has sharing as well in it's business edition. Alternatively, your scheme could work, but I'd add a pre-agreeded upon salt to it to prevent it being easily guessable. (e.g. "JimBob1272017tacos!!!" "JackJill2232018tacos!!!") – K.B. Dec 7 '17 at 19:25
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    Is email mandatory? It would be far simpler to let your documents live on some webserver that is protected by usernames and password for each account trying to access them. Assigning strong one time passwords to each document with all you constraints does not seem to be something that would scale nor run in the long term. – Patrick Mevzek Dec 7 '17 at 19:28
  • Cowthulu and K.B.: Yes, I did consider a password manager. IT does not want us using any cloud based password manager, and I'm very limited with what I can install on my computer, which is to say I can't install password manager that works offline. Patrick Mevzek: I agree that using a webserver would be far simpler, but unfortunately that is not permissible. As far as scale is concerned, since we are a small team and this scenario is fairly infrequent, scaling is not of high importance. – returnofthemac Dec 8 '17 at 18:55
  • I appreciate all the practical answers and solutions that have been brought forth. I was looking at this problem more from a theoretical standpoint. Given the constraints, is there an solution that allows me to just use passwords that only my team can guess, but still provide a modicum of security? – returnofthemac Dec 8 '17 at 19:14
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Making different passwords which are easily guessable adds no real security, but it does protect against accidentally reading a document intended for someone else. If that's all you need, great! Just concatenate the recipient name with a strong password known by the team.

But if you want to make it significantly difficult for teammates to snoop in documents not intended for them, I would suggest that you use asymmetric encryption together with secret sharing:

Encrypt each document so that it can be decrypted by either of two keys. The first key is the recipient's private key, and the other is a secret that requires two (or more) team members to uncover using the above-mentioned secret sharing.

This way, only the recipient can read the document, unless two or more team members together decide that they need access to it.

  • Thanks for the response FasAsGuest, and the Wikipedia article was a great suggestion. You are correct, security isn't of the utmost importance. The scheme was intended merely to prevent unintended people from accessing a document. Due to low technical proficiency among my colleagues, I doubt a more complex method (other than password protection) would be feasible. Encryption and keys would be beyond their capabilities, and would likely prove more difficult and burdensome than its worth, unfortunately. – returnofthemac Dec 8 '17 at 18:49
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Your scheme is inherently insecure. There is zero entropy present in the password, which is what determines a password's strength. You should expand on your business use cases and requirements - if you truely don't need to have secure documents this is fine, but it's trivial to compromise this type of security. From your requirements -

Easily understood (not too complicated/difficult to create the password) - Good
Password is not easily guessed - Failed, also very important.
Password is distinct for each document we send - Passes.
Easy for each of the team members to figure out (i.e. a team member can guess another team member's document's password) - Not applicable to passwords. If you only need knowledge of how a password is generated to guess it, you have an insecure password. This isn't an appropriate use case for passwords.

A better resolution would be to deploy a secure system such as an SFTP server that can be accessed by customers, clients, and employees. Use role based security to determine who can access what. This is a much better solution than this password scheme.

  • Thank you for your thoughts on the matter, Adonalsium. Undoubtedly the scheme is inherently insecure. The purpose of the scheme was to prevent people from easily opening documents they shouldn't. Truly secure documents is not necessary. I understand that there is zero entropy, but in this case a password is better than nothing (even if it is trivial to compromise). Unfortunately, SFTP is unavailable to me, and, as I've stated in response to FaxAsGuest, that would likely be too advanced for some of my colleagues. – returnofthemac Dec 8 '17 at 19:04

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