Yubico Forum

We are an IT company and have many many passwords that we need to keep track of for the various systems we use internally, vendor systems and client systems. How can I use yubikeys deployed to my users to build a password system that encrypts the passwords stored in the database, but allows the use of the yubikey to decrypt the password when requested?

I can't wrap my head around how the encryption will work. Traditionally, the yubikey is used only to verify that a person is who they say they are. I need to do more than that.

-Chris

Neat application.

Is this a central database or does each user have a separate set of secrets that need to be encrypted?

Central database of passwords, it'll be a web application. I can either encrypt once, or each time for each yubikey if I need to. I just don't know how to do the encryption. How can I use the yubikey to authenticate and encrypt the passwords for each user to view? I specifically want to require the yubikey each time a password is retrieved.

-Chris

Did you consider using the unique Yubikey ID (the first 12 chars of an OTP) to construct the encryption key to encrypt the user's passwords?

If you are concerned someone uses the Yubikey personalization tool to clone the same Yubikey ID as the user's, the clone's OTP validation would fail, unless they have the AES secret key you have.

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The YubiKey Server Guy

Good idea, but I want to use 256-bit CBC Rijndael, so I need a 32 byte key. I could pad the 12 characters from the Yubikey with static data, but that weakens the key doesn't it?

-Chris

Well, here is another problem. If I encrypt each password with each yubikey, when someone adds a new password they will only be able to encrypt it with their own key, so no one else can decrypt the password. Maybe I can setup the following chain:

User Key -> Master Key -> Password

Whereas, the master key encrypts the password, and the users' keys are used to decrypt the master key. Although the users' keys will not add any more security, as the weakest point of the system will be the master key; by using individual user keys, this will allow for revocation and I plan to never expose the master key to the user.

-Chris

Sounds a good idea to me in your use case! I suppose the Master key sits only in the backend, and preferably inside a h/w crypto device and never leaves it. Access to it requires a Yubikey plus maybe a personal PIN for authentication. User name is not necessary since from the Yubikey ID you know which user owns it.

Then by enforcing each Yubikey's access rights to certain accounts, you should be able to achieve the personalized experience, and maybe account sharing: Say if S is a shared account below, instead of emailing account-S password to everyone in your team, you can set it up like this:

* User-a uses Yubikey-a can access accounts A, S

* User-b uses Yubikey-b can access accounts B, S

Take a look at MashLife.com, it is a public web-based service for the similar purpose.

Best

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The YubiKey Server Guy

Assuming the master key encrypts all passwords, how can I use the yubikey to unlock unique encrypted master keys? The users will never see the master keys, but the program will use the user's key to decrypt the master key, then the master key to decrypt the password.

The problem I'm having is figuring out how I can use the yubikey to create a private key stored on the server, and use the yubikey to unlock that. Then, I can unlock the master key and the password. Each time the user requests to decrypt a password, they should be prompted for their yubikey.

-Chris

I'm seeing some Yubikey customers using Yubikey Token ID (the first 12 fixed chars of the OTP) + a user PIN to derive a "private" master key to encrypt all this user's credentials.

The cost is that when the user changes PIN or Yubikey all his/her credentials need to be re-encrypted. But the cost should be minimal if one user only has say < 100 accounts stored in the database.

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The YubiKey Server Guy