From bug 54948 comment 1:
Then to deal with existing hashes, we could provide a maintenance script to
convert both old-style and :A: hashes to :B: hashes or a future, work-hardened
successor (bug 28419).
This script should just convert from :A: to :B: hashes for now, and in the future it can be extended to whatever new password encryption method is chosen.
Version: unspecified
Severity: enhancement