We present fatal security flaws in the HALFLOOP-24 encryption algorithm, which is used by the US military and NATO. HALFLOOP-24 was meant to safeguard the automatic link establishment protocol in high frequency radio, but our research demonstrates that merely two hours of intercepted radio traffic are sufficient to recover the secret key. In the talk, we start with the fundamentals of symmetric key cryptography before going into the details of high frequency radio, HALFLOOP-24, and the foundation of our attack.