*** Shutting the phone down ensures a better level of security assurance since the encryption is using a strong password
*** Using a PIN for encryption generally renders the encryption useless as those can be cracked in seconds (see for example https://viaforensics.com/viaextract/viaextract-includes-android-encryption-cracking.html )
* Use TRESOR to store the secret key outside RAM.
** See http://www1.informatik.uni-erlangen.de/tresor for implementation on ARM.
* ChromeOS uses a slightly different disk encryption mechanism using eCryptFS.