+
+* Security consideration
+
+** `call-process-region' writes data in region to a temporary file
+
+`call-process-region' writes data in region to a temporary file.
+EasyPG does *not* use `call-process-region' to communicate with a gpg
+subprocess.
+
+** `(fillarray string 0)' is not enough to clear passphrases
+
+If Emacs crashed and dumps core, passphrase strings in memory are also
+dumped within the core file. `read-passwd' function clears passphrase
+strings by `(fillarray string 0)'. However, Emacs performs compaction
+in gc_sweep phase. If GC happens before `fillarray', passphrase
+strings may be moved elsewhere in memory.
+
+Fortunately, there is gpg-agent to cache passphrases in more secure
+way, so the EasyPG library dares *not* to cache passphrase by itself.
+Elisp programs can set `epg-context-passphrase-callback' to cache
+user's passphrases.