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Locksmithing Locksmithing Presentation Transcript

  • Overview of Locksmithing
    • Splash! 2007 (November 18)
    • Sho Uemura (meeg@mit.edu)
  • What is locksmithing?
    • The science and art of making and defeating locks
    • Lockpicking uses knowledge of lock design
    • Lock design uses knowledge of lockpicking
  • Why study locks?
    • Not because it’s useful (it’s not)
    • Know the law and be ethical
  • Lock design
    • The purpose of a lock is to make something more accessible to the owner than to attacker
    • Convenience: minimize difficulties for owner
    • Security: maximize difficulties for attacker
    • Lock must be cheap and durable
    • Lock must be easy and fast to open
    • Key/combination must be easy to carry
    • Design should be expandable
    • Picking the lock must take time, training and tools (the three T’s)
    • Method of entry should not be reliable and repeatable (the two R’s)
    Principles of design
  • Lockpicking
    • Every technique relies on one weakness of the design: the dominant imperfection
    • Two methods: “mind” and “hand”
    • “ Mind”: fool the lock into thinking you have the key
    • “ Hand”: use weaknesses in design to bypass lock security
  • Pin tumbler lock
    • Most common type of key lock today
    • Cheap, mass-produceable, durable, compact
    • Many variations, but basic principle is the same
    • Key has cuts of varying depths
    • Lock has spring-loaded pins that contact the key
    • If all pins are at the correct heights, cylinder turns
    Pin tumbler internals
  • The sequencing defect
    • Locks are designed to test key/combination at multiple points simultaneously
    • Imperfect manufacture -> some points are tested before others
    • Guess each point in sequence to pick a lock
    • 100000 combinations, but only 50 guesses
  • Picking a pin tumbler lock Ideal lock: all pins are same size, and holes are in a straight line; all pins must be set at the same time to open lock Reality: some pins will bind in their holes before others; this creates a sequence in which the pins can be picked
  • How to crack a lock
    • Bypass the lock
    • Use “magic”
    • Decoding
  • Opening locks with magic: bumpkeying
    • Hit the bottom of a pair of pins, and the top pin bounces up; a gap is created
    • Hit all the pins at once, and the gaps allow the cylinder to turn!
  • Bypassing a lock
    • Push the bolt back: shimming (for padlocks), carding and sliding (for doors)
    • Remove the lock
    • Open door from inside
  • Shortcuts
    • Drill holes in a lock to see combination or break pins
    • “ Read” previously dialed combination
    • Research lock type - limited combinations, preset combinations, key cut depths
    • Skeleton keys
  • Common design improvements
    • Sidebars
    • Security pins
    • Pin-in-pin locks
    • Tubular pin tumbler lock
    • Same principle as pin tumbler, but pins lie in a circle
    • Advantage: lock must be picked 6-8 times to unlock
    • Disadvantage: pins are more exposed
    • Flaw: Impressioning
    Tubular lock
  • Impressioning a tubular lock
  • Multiple-dial combination lock
    • Combination is a string of dial positions
    • Bolt has teeth touching dials
    • Correct combination aligns gates in dials with the bolt
  • Multiple-dial combination lock
    • Sequencing: Since the bolt contacts some wheels before others, each wheel’s gate can be found to open the lock
    • Decoding: A thin piece of plastic can feel the gates in the wheels directly
  • Single-dial combination lock
    • Cheap, simple; very popular
    • Can be very secure; used in most safes
  • Single-dial combination lock
    • Combination is series of dial rotations
    • Dial pushes wheels inside lock
    • Correct combination aligns each wheel with fence
  • Lock manipulation
    • Uses the sequencing defect
    • Ideally, all wheels contact the fence
    • If one wheel sticks out, the fence will drop down at that wheel’s gate; this identifies that wheel’s combination
    • Repeat for all wheels to get combination
  • Warded lock
    • Oldest type of lock (Ancient Rome)
    • Easy and cheap to make
    • Insecure
    • Key has notches of varying shapes in varying places
    • Lock has wards blocking the key’s path
    • If notches correspond to wards, key can rotate through to push a bolt
    Inside a warded lock
  • Lever tumbler lock
    • Evolved from warded lock
    • Chubb detector lock is still one of the best locks ever designed
    • Complex, bulky, fragile and expensive
    • Key has bittings of varying heights
    • Lock has levers with cuts in varying positions
    • Bolt is released when all levers are raised to the correct position
    Lever tumbler lock
  • Further reading
    • MIT Guide to Lockpicking
    • Wikipedia
    • OldLocks.com
    • “ Locks, Safes and Security” by Marc Weber Tobias
    • Crypto.com - Matt Blaze