When a system must go from a powered down state to a fully operational state wit

Question

When a system must go from a powered down state to a fully operational state without any human intervention it therefore needs access to usable authentication credentials unattended. The system must recover and boot automatically without human intervention so the credentials must be stored in a readable format on the file-system.

We hear about passwords being hashed(+salted) at rest and encrypted in transmission but is encoding acceptable under the above scenario? For instance I was reading an article about WebSphere where they encode their system passwords using XOR and base64 and consider it as the best option.

Encrypting WebSphere Application Server system passwords

Explanation / Answer

In the case of WebSphere, they appear to define "encoding" as "unkeyed encryption" -- encryption where the security comes from the secrecy of the algorithm rather than secrecy of a key.

For system credentials on a computer that needs to start up unattended, there isn't much practical difference between the two. In both cases, all the secret information is present at all times, and security comes from keeping attackers from being able to access those secrets: if an attacker can access the encrypted/encoded system credentials, they are almost certainly able to access the master key (encryption) or the decoding algorithm (encoding).

There are ways to protect the key in the case of encryption (TPM modules, smart cards), but since the system can start up unattended, an attacker can probably use them as a black box to decrypt the system credentials without needing to know the master key.

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