[Bitcoin-development] Wallet encryption migration

[Luke-Jr]

Just wanted to get these suggestions out here:
1. Write over the old, unencrypted wallet.dat a couple of times with pseudo-
   random data in an attempt to secure-delete it.
2. Mark all the keys imported from an unencrypted file (wallet or otherwise)
   as "potentially compromised" and never use them for new addresses
   (basically, don't use the old keypool for getnewaddress, change, and such).