Who inherits my passwords?

[handslive]

This is a problem I've been thinking about a lot.  I have a significant list of passwords, PINs, passphrases, and bits of profile information for the sites and applications they get used on.  My partner (or at least my estate) should have access to the most up to date version of this information.  It gets changed regularly and this means a safe deposit box isn't really the best choice.  What I need is a kind of digital escrow service that I don't have to hand my keys over to.

Earlier this year, I read a bit about k-of-n secret sharing and even found a site on the Internet with code for generating shared secrets.  The author has a demo of this as well.  I've been thinking about ways that this could be used to make a digital sealed envelope available.

The first question is what would the secret be that gets shared among the participants.  One possibility is to use a hex or base64 representation of a symmetric AES key.  The key could be used to decrypt a file containing the information.  A variation on this would be to use the private key from a public-private key pair.  Distribute the public key and the shared secrets.  Together they can be used to construct the key pair used by PGP or GPG to access an encrypted file or message.  Most utilities for encrypting files, though, expect the keys to be protected in storage using a passphrase.  PGP, WinZip, and all of the different password vault programs I've used support the use of a full sentence if you want.  This secret phrase could be protected instead and a copy of the program and encrypted file provided.  This last option is the easiest if you're looking for a way of doing this that doesn't require building special tools and lets people use whatever they're most comfortable with.

The next question is how you manage the generation, updating, and distribution of the shared secrets.  I can think of three approaches off the top of my head.  Most other approaches would be variations of these, I think.  First, a central web site that allows the participants to track the different shared secrets they've been given (I'm assuming that, if I did this, I would also be doing the same for the other participants).  Second, an application that can be run locally for storing secrets and potentially the encrypted file as well.  Third, just developing a manual process for doing this and letting people use whatever file formats and a storage methods they want.

I'm an anal kind of guy, so here's my pros and cons for each approach.

Web site
Pros:

• generation and distribution could be contained to the application
• management of the secrets and updating would be centralized

Cons:

• the web site would be a tempting target since it contains all the shared secrets
• encryption and key management for storage of the secrets is needed to minimize this threat
• site would need to be over HTTPS to ensure confidentiality (not horrible, but needs to be said)
• application needs to support proper segregation of duties and auditing of both user and administrator actions

I don't care for this option because it's clearly expensive to setup and run properly.

Desktop application
Pros:

• distributes the risk of compromise, which is closer to the original intent of this kind of approach

Cons:

• communicating the shared secrets to each user requires care and attention; you wouldn't want all the secrets to be in your sent-mail folder or something but you have to be sure each user gets an accurate copy of the secret that they can save away somewhere
• I'd want the application to be for multiple platforms because my circle of physically proximate friends may choose to run different platforms.  I'm thinking Windows XP, Windows Vista/7, OS X, and some Linux variant.  (Makes me lean towards Java as the language of choice because I'm lazy.)
• still probably need to think about encrypting the collection of shared secrets in storage, so there's some key management involved even so

This isn't a terrible option, but I am lazy.

Manual process
Pros:

• easy implementation, tailored to each participant

Cons:

• if the implementation is unique to each participant, the level of security for the shared secrets will also be "unique" to each; not a huge minus, but not a plus either
• the process itself has to be simple to understand and follow for it to work given that some participants may be less technically inclined than others

I obviously lean towards this solution, but I do need to think about what the simplest, safest process for doing it would be.  I'd like to at least be able to provide the secret generation method in a common location so we wouldn't be dependent on the author's web site.  He provides a command line version for Linux.  In fact, I believe his PHP demo invokes the command-line version.

Comments

[hobbitbabe.livejournal.com]

I am glad that people like you are considering this stuff, because I don't know how to assess it well enough to be comfortable with it at all.

My mother did not have what I consider normal boundaries for a 21st century person. She once wanted to send me to the bank with her PIN, for example. And the night before we expected my father to die, she went to the bank and took all the money out of his (non-joint) account, because she knew his PIN too. We knew all her relevant passwords and answered her emails while she was ill. All of this was convenient at the time, but there is no way that I would do anything like that, without some better protection for me and for my digital executors.

[puppytown.livejournal.com]

Gosh, I could have sworn I'd heard of a similar service, but all I can find is http://keepass.info/.

Anyway, yes. Yes yes yes. Sooooo need this.

[handslive.livejournal.com]

Well, KeePass is one of the tools I've used for storing passwords, but it doesn't have two of the key features my above idea has. First, there's no good way to insist that two or three people need to get together to recover access short of just splitting the passphrase up. Second, such a splitting scheme doesn't recover easily from the loss of some of the participants, like car crashes or house fires.

[puppytown.livejournal.com]

Agreed! The thingy I'd heard of had some kind of interesting delegate options. I dunno where I read about it, now. Need to review my starred items in Google Reader, maybe.

[handslive.livejournal.com]

I'd be interested to read more about it if you find the link.

[puppytown.livejournal.com]

Maybe: http://mashable.com/2010/04/07/entrustet/

[handslive.livejournal.com]

Interesting. I have some thoughts, but I probably need to do some more reading and make a whole separate post. :-)

[buhrger]

the notion of appointing a "digital executor" occurred to me a while ago. if one's willing to entrust the entirety of one's physical estate to the oversight of a single individual (the ordinary executor), entrusting one's data to such a person (although not necessarily the same person) doesn't seem to me much of a greater risk.

but it's something i think about. i'd say more, but gotta run very soon. neat post!

[handslive.livejournal.com]

It's one thing to hand over control as one might with a power of attorney or as one must with an executor, but the assumption that's built in is that I am no longer directly involved in the management, use, or development of my resources.

This is quite a different level of trust if I am actively involved and have handed over equivalent control to another person. I see those as vastly different trusts.

[buhrger]

ah. yes, it is.