Veinprint lock

A veinprint lock is a type of biometric security system used by the Covenant. Whereas most biometric systems use fingerprints or facial profiles for a key, a veinprint lock reads the size and shape of the blood vessels in a user's body, usually in a wrist or a finger. Because of their ease of use and the difficulty in spoofing them with a fake, veinprint locks are considered to be the gold standard for security systems, and are affordable by the upper half of Covenant society.

Use and Limitations
Veinprint locks use an optical scanner to measure a sample of tissue and construct a three dimensional map of the veins within. This map is then compared to a key stored in the lock's encrypted memory, usually cued by a secondary source of identification such as a signet ring or a tattoo. The key and the examined tissue must share identical features such as the presence and relative position of venous branches and valves, or the sample will be rejected and the system will refuse to unlock.

Spoofing a veinprint lock is a very difficult task. An organic limb with its complex network of blood vessels is exceedingly difficult to fabricate, and all but the most basic veinprint locks are sensitive enough to reject twins and genetic clones. It is commonly believed among the Covenant that only the original limb, severed from its owner, will spoof the lock. Indeed, this is a plot point in countless novels and stageplays. However, blood rapidly deoxygenates when it is not in circulation, and it is trivially easy for a scanner to spot the difference. The useful life of a severed limb is measured in seconds.

The tools to create forgeries do exist, though they are usually only within the reach of powerful criminal organizations and wealthy cat burglars. These tools usually craft a forgery from gene-tailored tissue and synthetic blood within the span of an hour, and the forgery lasts half a day before necrosis sets in. Often, it is easier to simply hack the lock with electronic tools, and of course any lock is only as good as the door it secures.

History
Most starships and warehouses owned by the Clan 'Umtalla on High Charity were protected by veinprint locks. During the Fall of High Charity, Jiralhanae forces attempted to use the severed arms of the Sangheili residents to access these, and were unsuccessful until they forced a captured P'thon 'Umtalla to unlock them.

List of appearances

 * Not All Who Wander