I would hope that a system competent enough to migrate to bcrypt would also be competent enough to rehash the entire database as well. Logins check bcrypt(oldHa

I would hope that a system competent enough to migrate to bcrypt would also be competent enough to rehash the entire database as well. Logins check bcrypt(oldHash(pw)); if it matters they can be updated to bcrypt(pw). Of course, "Hope is not a strategy".