Two - man rule The two - man rule is a control mechanism designed to achieve a high level of security for especially critical material or operations . Under this rule all access and actions requires the presence of two authorized people at all times . Nuclear weapons . Per US Air Force Instruction ( AFI ) 91 - 104 , " The Two Person Concept " is designed to prevent accident al or malicious launch of nuclear weapon s by a single individual . In the case of Minuteman missile launch crews , both operators must agree that the launch order is valid by comparing the authorization code in the launch order against a " Sealed Authenticator " ( a special sealed envelope which holds the code ) . These Sealed Authenticators are stored in a safe which has two separate lock s . Each operator has the key to only one lock , so neither can open the safe alone . Also , each operator has one of two launch keys ; once the order is verified , they must insert the keys and turn them simultaneously . A total of four keys are thus required to initiate a launch . For additional protection , the missile crew in another Launch Control Center must do the same for the missiles to be launched . As a further precaution , the slots for the two launch keys are positioned far enough apart to make it impossible for one operator to reach both of them at once . On a submarine , both the commanding officer and executive officer must agree that the order to launch is valid and then mutually authorize the launch with their operations personnel . Instead of another party who would confirm a missile launch as in the case of land - based ICBM s , the set of keys is distributed among the key personnel on the submarine and are kept in safes ( each of these crew members has access only to his or her keys ) . Some keys are stored in special safe s on board which are secured by combination lock s . Nobody on board has the combination to open these safes ; the unlock key comes as a part of the launch order from the higher authority . Higher up , in the United States , the National Command Authority comprising the President and Secretary of Defense must jointly issue the order to use nuclear weapons to the Chairman of the Joint Chiefs of Staff . Usually , the two - man rule is also backed up with hardware and software measures including command code verification and command keys . Journalist Ron Rosenbaum has pointed out that , once the order is issued , the process is entirely concerned with authenticating the identity of the commanding officers and the authenticity of the order , and there are no safeguards to verify that the order or the person issuing it is actually sane . Notably , Major Harold Hering was discharged from the Air Force for asking the question , " How can I know that an order I receive to launch my missiles came from a sane President ? " Cryptographic material . Two - person integrity ( TPI ) is the security measure taken to prevent single - person access to COMSEC keying material and cryptographic manuals . TPI is accomplished as follows : At no time can one person have in his or her possession the combinations or keys to gain lone access to a security container or cryptographic equipment containing COMSEC material . Neither can one person have sole possession of COMSEC material that requires TPI security . No - lone zone . A no - lone zone is an area that must be staffed by two or more qualified or cleared individuals . Each individual must be within visual contact with each other and in visual contact with the critical component that requires a no - lone - zone area designation . A no - lone zone may contain a cryptographic component , weapon system hardware under test , a nuclear weapon or active nuclear weapon controls . In the USAF concerning critical weapons , it is a zone in which the presence of a single individual is prohibited . The two - person concept ( or policy ) is in effect in which two individuals , knowledgeable of the task to be performed , and capable of detecting an incorrect or unauthorized procedure on the part of the other in reference to the task being performed . Other uses . The two - man rule is used in other safety critical applications where the presence of two people is required before a potentially hazardous operation can be performed . This is common safety practice in , e . g . , laboratories and machine shops . In such a context , the additional security may be less important than the fact that if one individual is injured the other can call for help . As another example , firefighters operating in a hazardous environment ( i . e . interior structure fire , HAZMAT zone , also known as IDLH ) function as a team of at least 2 or more personnel . There are commonly more than one team in the same environment , but each team operates as a unit . Some software systems enforce a " two - man rule " whereby certain actions ( for example , money wire transfers ) can only take place if approved by two authorized users . Dual keys require the authorization of two separate parties before a particular action is taken . The simplest form of dual key security is a lock that requires two keys to unlock it . The two keys would be in the possession of two separate persons . The lock could only be opened if both parties agreed to open it and at the same time . Canada accepted having American W - 40 nuclear warheads under dual key control on Canadian soil in 1963 to be used on the Canadian BOMARC missiles . In business , the four - eyes principle " means that all business decisions and transactions need approval from the CEO and CFO . Since the CFO is not reporting to the CEO , there is an independent controlling mechanism in place . " Similarly , many banks implement some variant of the two - man rule to secure large sums of money and valuable items . Under this concept , unlocking the vault requires two individuals with different keys if the vault is secured by a key lock system . For bank vaults secured by combination lock , one individual will know half of the combination and a second person will know the remaining half . At no point will either person know the other person ' s half of the lock combination , requiring both persons to be physically present in order to unlock the vault . As an extension of the broader rationale for the " two - man rule " , regulations for some companies or not - for - profit organizations may require signatures of two executives on checks . These rules make it harder for an individual acting alone to defraud the organization . In popular culture . In the film " The Hunt for Red October " , when Captain Ramius takes the dead political officer ' s missile key , a fellow officer , the ship ' s doctor , requests that he have the key , using the two - man rule as his reason , saying " The reason for having two missile keys is so that no one man may arm the missiles . " The two - man rule was crucial in the movie " Crimson Tide " when the captain and the executive officer of the " USS Alabama " disagreed over the release of nuclear weapons . In the Tom Clancy novel " The Sum of All Fears " President Robert Fowler and Jack Ryan , as Deputy Director of the Central Intelligence Agency , comprise the two men that were to issue a nuclear launch order against a city thought to be harboring a terrorist leader . Ryan refused to validate the launch order and the nuclear attack is aborted . Ryan was serving as the second man because the Secretary of Defense was killed in a terrorist attack . In the film " WarGames " , two missile officers are given a launch order , leading to one drawing his sidearm on the other when the latter refuses to turn his launch key . Unknown to them , the attack was a simulation and this incident ( as well as a significant rate of similar refusals among other missile crews ) sets up the basis of the movie , in which the Department of Defense replaces the two - man system with the WOPR computer to prevent a future refusal to launch . Similar to " WarGames " , in " " one officer pulls a gun on the second officer when given the command to launch nuclear missiles . However , this is not due to a disagreement , but due to direct mind control . In the film " Salt " , the President together with the Secretary of Defense verified the authentication codes alternately to launch nuclear weapons from the nuclear football inside the Presidential Emergency Operations Center . The " Star Trek " franchise depicts the two - man rule and other similar variations in critical situations , often concerning arming or cancelling a ship ' s self - destruct mechanism . Some variants require the authorization of " three " senior officers ( " " , " " ) , others just the commanding and executive officers ( " " episodes " 11001001 " and " Where Silence Has Lease " , " " episode " " ) . All depictions include voice authorization of the officers involved , while the two - man variant also involved a hand print identification . In Infinity Ward ' s game " " , the main character uses a similar two - man key to launch a hijacked Russian submarine ' s missiles against its own fleet . In " Torch of Freedom " by Eric Flint , the nuclear self - destruct device for an important installation requires at least two people to activate . Nonetheless , one person gains access to all the necessary codes and is able to activate the device . In the first episode of the ABC series " Last Resort " captain Marcus Chaplin and XO Sam Kendal perform a two - man launch procedure , prior to questioning the attack order .