Symmetric key storage

Question

My company is going to be storing sensitive data for our customers, and will be encrypting data using one of the managed .NET encryption algorithm classes. Most of the work is d

Answer 1

There only two real solutions for (the technical aspect of) this problem. Assuming it's only the application itself that needs access the key...

1. Hardware Security Module (HSM) - usually pretty expensive, and not simple to implement. Can be dedicated appliance (e.g. nCipher) or specific token (e.g. Alladin eToken). And then you still have to define how to handle that hardware...

2. DPAPI (Windows Data Protection API). There are classes for this in System.Security.Cryptography (ProtectedMemory, ProtectedStorage, etc). This hands off key management to the OS - and it handles it well. Used in "USER_MODE", DPAPI will lock decryption of the key to the single user that encrypted it. (Without getting too detailed, the user's password is part of the encryption/decryption scheme - and no, changing the password does not foul it up.)

ADDED: Best to use DPAPI for protecting your master key, and not encrypting your application's data directly. And don't forget to set strong ACLs on your encrypted key...

Answer 2

In response to #3 of this answer from the OP

One way for authorized members to be able to view the encrypted data, but without them actually knowing the key would be to use key escrow (rsa labs) (wikipedia)

In summary the key is broken up into seperate parts and given to 'trustees'. Due to the nature of private keys each segment is useless to by its self. Yet if data is needed to be decrypted then the 'trustees' can assemble thier segments into the whole key.

Answer 3

I think I misunderstood your question. What you're asking for is not in scope of how the application handles its key storage, but rather how your company will store it.

In that case, you have two obvious choices:

• Physical: Write to USB drive, burn to CD, etc. Store in physically secure location. But you run into the recursive problem: where do you store the key to the vault? Typically, you delegate 2 or more people (or a team) to hold the keys.

• Software: Cyber-Ark Private Ark is what my company uses to store its secret digital information. We store all our admin passwords, license keys, private keys, etc. It works by running a Windows "vault" server that is not joined to a domain, firewalls all ports except its own, and stores all its data encrypted on disk. Users access through a web interface that first authenticates the user, then securely communicates with the vault server via explorer-like interface. All changes and versions are logged. But, this also has the same recursive problem... a master admin access CD. This is stored in our physical vault with limited access.