[rdiff-backup-users] backing up a Bitcoin wallet (private key)

[Grant]

I was planning to back up my Bitcoin wallet (private key) along with
the rest of my system backups which are versioned by rdiff-backup.
However, it occurred to me that if the password with which my wallet
is encrypted is deemed non-secure at some point and I change that
password, the rdiff-backup repository will still contain the private
key encrypted with the non-secure password.

Am I thinking this through correctly?  If so, can I delete all
versions of a particular file from an rdiff-backup repository?

- Grant