I totally empathise with Ian's frustration. I myself spent eight hours trying to circumvent this 'bug', to put it mildly. I tried to follow a half-dozen contradictory, inaccurate and incomplete walkthroughs with no success, so I'm giving up and starting from scratch.
The walkthrough at http://wiki.debian.org/DebianInstaller/Rescue/Crypto does not exist. As this bug hasn't been addressed in 8 years, it may be worth giving up on it. If so, there should at least be bold warnings to anybody tempted to set up encrypted volumes that they will not be reusable if one needs to reinstall Debian unless they have highly advanced knowledge of hand-writing configuration files from rescue CDs. This would, at least, stop hundreds of aggregate human hours from being wasted. -- To UNSUBSCRIBE, email to debian-bugs-rc-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org