If a group planned ahead they could give out some secondary kind of key. Gmail gives out these really long codes I can use to login should I not have the authenticator app.
Sorry, I might be missing something here, but would there be any tangible differences between the service provider having access to a secondary key vs them having access to the primary key if both can be used to access your data?
I'm honestly interested because I'm building a distributed system where only the user has the decryption key, and I've always just assumed that password recovery is a lost cause in such systems.
I would assume the recovery key is not stored in plain-text - it's likely hashed, similar to a password. If you need to use it, you enter the (hopefully safely stored) recovery key you have, they re-hash it and compare to the hashed one they keep.
I believe it is the only way if you truly want a single user to have complete control of decryption. There are other solutions if you don't. I heard of one the other day (from MaidSafe maybe?) where you have a shared secret amongst your "friends" and if a quorum of them agree, it can reset your password. I assume this means your data is duplicated and encrypted via that shared secret as well which could be coerced I suppose.
Not if you make the users password the key.