Notes/doc/0001-Welcome to Trilium!/0000-Protected notes.html

<p>Protected notes are encrypted using AES encryption algorithm where encryption
  key is generated using Scrypt key derivation function from user entered
  password.</p>
<p>&nbsp;</p>
<p>You can either protect individual notes or whole subtree by right clicking
  on an item in the tree pane. In such a case it's still a case of all of
  the notes being encrypted individually. One consequence is that you can
  still create unprotected notes under protected notes.</p>
<p>&nbsp;</p>
<p>In protected notes, only note title and note text are encrypted. All metadata
  like date of last modification, note structure etc. are not encrypted and
  can be visible even without entering protected mode.</p>
<p>&nbsp;</p>
<p>When you try to perform action which requires protected session (e.g.
  reading protected notes or making note protected), you'll be asked to enter
  password. After successful authentication, protected session is established
  for limited period of time (by default 10 minutes). If protected session
  is not refreshed during this time, protected session expires and user needs
  to authenticate again to start new protected session.</p>