Once you have generated your master PGP key, will the "data" in the private key ever change?

For instance, if you add another subkey, uid, or any other data to the master key, do these changes need to be "written" to the "secret half of the key", modifying it in any way? Or are all changes made to the "public half of the key", or even some sort of third signed file with the details?

That is, can you store the secret key on read-only media such as a CD-ROM, printed on paper, or tattooed onto the shaved head of one of your servants?

Yes they are still vulnerable. Encryption just transforms a sequence of bits into another sequence of bits (and assuming the encryption is good it will be computationally infeasible to reverse this process without knowledge of some secret). There's no reason why encryption can't be performed again on an already encrypted sequence of bits.

It's possible certain ransomware implementations might look for specific files that are likely to be of high value, and encrypting these files might make them more difficult to recognise. However, I would not depend on this as my primary control against the threat of ransomware.
