M-209
= M-209
{wiki=M-209}
The M-209 is a portable cipher machine used by the United States military during the Cold War for encrypting and decrypting classified messages. It was designed to be lightweight and easy to use, making it suitable for field use by operators who needed to secure their communications. The M-209 works based on a mechanism involving gears and rotors, which create a complex system for encrypting messages.