How to operate with base64

Encode file:
$ base64 message.file > message.file.base64

Decode file:
$ base64 --decode message.file.base64 > message.file

Encode string:
$ echo "open message" | base64 > message.base64

Decode string:
$ echo "b3BlbiBtZXNzYWdlCg==" | base64 --decode > message.file

How to modify text files

Remove newline (\n) character:
$ tr -d "\n" < file.original > file.new

Replace newline (\n) character:
$ tr "\n" " " < file.original > file.new