The Football
It follows the President where ever he goes and is never more that a few steps from his side. It is carried by a military officer who must undergo the nation's most rigorous security background check - the "Yankee White". It contains a secure SATCOM radio and handset, the nuclear launch codes known as the "Gold Codes" and the President's Decision Book - the nuclear playbook that the President would rely on if he would ever have to decide to use nuclear weapons. Its real name is unknown but it is popularly known as "the football".
The concept of the football came about in the aftermath of the Cuban Missile Crisis. President Kennedy was concerned that some Soviet commander in Cuba might launch their missiles without authorization from Moscow. After the crisis, Kennedy ordered a review of the U.S. Nuclear Command and Control system. The result was the highly classified National Security Action Memorandum that created "the football".
The White House Communications Agency which oversees the military unit in charge of "the football", was created with personnel from sections of the Defense Communcations Agency, composed of units from the Defense Communications Operations Unit (responsible for communications and emergency power engineering) and the Defense Communications Support Unit. To work in these units, a candidate must pass a special security investigation, called "Yankee White." The criteria include U.S. citizenship, unquestionable loyalty, and an absolute absense of any foreign influence over the individual, his family, or "persons to whom the individual is closely linked." The aide who carries "the football" comes from the five military branches and is at the rank of O4. (Major for U.S. Army, U.S. Air Force, and U.S. Marine Corps), or Lt. Commander for Navy and Coast Guard. They must be knowledgeable about all aspects of the overall SIOP, as well as the various options available to the President for implementing the war plan.
Lieutenant Commander Vivien Crea became the first woman from any service, as well as the first servicemember from the US Coast Guard to serve as the Presidential Military Aide. She carried the "football" for President Ronald Reagan for three years.
SIOP strategic targeting involves four groups:
The "Black Book" is said to contain 75 pages of options, to be used against these four primary groups. The options are further divided into:
Major Attack Options (MAO's)
Selected Attack Options (SAO's)
Limited Attack Options (LAO's)
The SIOP also allows the President to select Regional Nuclear Options (RNO's) for use against enemy forces leading a conventional attack against U.S. forces. These plans allow the President to execute the SIOP during an attack. He may decide to activate Launch on Warning (LOW) or Launch under Attack (LUA) plans in the event an actual nuclear attack.
The National Security Agency is in charge of distributing the daily Gold Codes to the White House, Pentagon, STRATCOM, and the TACAMO aircraft. Use of the Gold Code constitutes an order to execute the SIOP by the National Command Authority (NCA). The National Command Authority (NCA) consists of the President, the Secretary of Defense, or their duly deputized alternates and successsors.
https://www.globalsecurity.org/wmd/systems/nuclear-football.htm