opensslコマンドで簡単なファイル暗号化 ref: http://qiita.com/ikuwow/items/1cdb057352c06fd3d727

file0.txt

$ openssl aes-256-cbc -e -in rawtext.txt -out encrypted.txt
enter aes-256-cbc encryption password: # パスワード入力
Verifying - enter aes-256-cbc encryption password: # もう一度

file1.txt

$ openssl aes-256-cbc -e -in rawtext.txt -out encrypted.txt -pass file:./password.txt

file2.txt

$ openssl aes-256-cbc -d -in encrypted.txt -out decrypted.txt
enter aes-256-cbc decryption password: # パスワードを入力

file3.txt

$ openssl aes-256-cbc -d -in encrypted.txt -out decrypted.txt -pass file:./password.txt