The secret spend key is kept encrypted in memory, and
decrypted on the fly when needed.
Both spend and view secret keys are kept encrypted in a JSON
field in the keys file. This avoids leaving the keys in
memory due to being manipulated by the JSON I/O API.
Previously, a file containing the unencrypted Monero address was
created by default in the wallet's directory. This file might pose
as a privacy risk. The creation of this file is now opt-in and can
be enabled by providing
--create-address-file
