> if the 10x-wipe retries counter is unencrypted, it will be broken by third-parties
It can't be encrypted with the same key as the rest of the harddisk, or it wouldn't be possible to increase it on a failed decryption attempt. But even if it is, you can always restore a previous state from backup.
To be honest, I still don't understand who the FBI can't brute force it (other than the time it would take), and how Apple's assistance could possibly help, if the encryption was done well.
It can't be encrypted with the same key as the rest of the harddisk, or it wouldn't be possible to increase it on a failed decryption attempt. But even if it is, you can always restore a previous state from backup.
To be honest, I still don't understand who the FBI can't brute force it (other than the time it would take), and how Apple's assistance could possibly help, if the encryption was done well.