How Enigma was cracked

00:19:29
https://www.youtube.com/watch?v=zCn3GCOwmeI

概要

TLDRIn hierdie video reeks verken ons die werking van die Enigma-masjien en die Bombay-masjien, wat van nuuts af gebou is om die innerlike werking van hierdie masjiene te verstaan. Die Enigma-masjien het 'n unieke bedradingsmeganisme wat verseker dat geen letter in die masjien na homself kan omskakel nie, wat nek toe 'n swakheid bied vir kodebreek. Alan Turing en sy span het hierdie swakheid benut deur 'Cribs' of gasteboodskappe te gebruik om geskikte letter kombinasies te vind. Die video bespreek hoe die Bombay-masjien ontwerp is om die Enigma se rye, rotors en stekker bordinstellings doeltreffend te verken en hoe dit vinniger kan werk as tradisionele metodes. Dit sluit 'n detailbespreking van die elektrisiteitsstroombane van die Bombay-masjien in, sowel as 'n demonstrasie van hoe om die rotors te optimale en die plug bord te analyseer. Die einddoel is om die Enigma se kodering met 'n meer gesofistikeerde benadering as ooit tevore te verbreek.

収穫

  • 🛠️ Die Enigma-masjien gebruik 'n unieke bedradingsmeganisme.
  • 💡 Geen letter kan in die Enigma-masjien na homself verander nie.
  • 🔍 Alan Turing het die swakhede van die Enigma ontgin.
  • 📜 'Cribs' help om geskikte letter kombinasies te vind.
  • ⚙️ Die Bombay-masjien is ontwerp om die Enigma se instellings te verken.
  • 🔌 Die olie masjien gebruik rotors en 'n stekker bord.
  • ⚡ Skakels in die Bombay-masjien laat vinniger resultaat toe.
  • 🔄 'Loops' in die Crib bring 'n tweede swakheid na vore.
  • 📈 Die Bombay-masjien optimaliseer die kodebreekproses.
  • 🔭 Die video demonstreer die werksmetodes van die masjiene.

タイムライン

  • 00:00:00 - 00:05:00

    Die video begin met 'n bespreking oor hoe die Enigma-masjien werk en die eerste gebrek aan die masjien wat die wiskundiges by Bletchley Park gebruik het om die kode te breek. Deur die werking van die Enigma te ontleed, sluit dit die spesifieke proses in wat betrokke is wanneer 'n sleutel gedruk word, wat lei tot die insig dat geen letter na homself gekonverteer kan word nie, wat 'n potensiële swakheid bied om te benut.

  • 00:05:00 - 00:10:00

    Die volgende stap is om te verduidelik hoe die verstekboodskap, genaamd 'n crib, gebruik word om te sien watter letters van die ingewilligde boodskap en die geskatte boodskap ooreenstem. Ten slotte word die werkings beginsels van die Bombay-masjien voorgestel, wat gebaseer is op 'n een-tot-een ooreenstemming wat vasgestel is van letters van die twee boodskappe, wat dan benader kan word om die Enigma in te breek.

  • 00:10:00 - 00:19:29

    Die video fokus daarna op die ontwerp en werking van die Bombay-masjien, waarvoor die ingenieurs dit ontwikkel het om die Enigma se kode effektief te breek. Dit sluit 'n verdiepende analise van die rotor posisies en die bou van die elektrisiteit sirket in, wat die nodige konneksies en kragtoestande uitlewer. Die finale stap is om die spesifieke lokke in die crib te identifiseer wat benut kan word om die Enigma se kode te breek en verskaf 'n stap-vir-stap riglyn vir die proses.

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  • 00:00:02
    how did the Enigma machine work
  • 00:00:06
    how did Alan Turing break the Enigma
  • 00:00:08
    using the Bombay machine
  • 00:00:10
    in this series of videos we explore the
  • 00:00:12
    Enigma machine and the Bombay machine
  • 00:00:14
    which we have built from scratch in a
  • 00:00:16
    virtual environment so that we can
  • 00:00:18
    actually see them working inside out and
  • 00:00:20
    understand every aspect of these
  • 00:00:22
    incredible machines
  • 00:00:26
    welcome to ingenious
  • 00:00:28
    [Music]
  • 00:00:37
    in the last episode we have seen how the
  • 00:00:39
    Enigma machine worked by examining the
  • 00:00:41
    machine right down to every single wire
  • 00:00:43
    switch and light bulb
  • 00:00:46
    now we will explore how the same Enigma
  • 00:00:48
    machine was cracked by the
  • 00:00:49
    mathematicians at The Bletchley Park
  • 00:00:53
    [Music]
  • 00:00:55
    if you recall the Enigma machine uses
  • 00:00:57
    two contact switches in its keyboard
  • 00:01:00
    when the key is pressed the switch
  • 00:01:02
    output wire connects to the battery's
  • 00:01:03
    positive terminal
  • 00:01:05
    when the key is not pressed the switch
  • 00:01:07
    output wire connects to the light bulb
  • 00:01:10
    in this case key for letter e is pressed
  • 00:01:13
    and light bulb for letter T is glowing
  • 00:01:16
    notice here that the current reaches
  • 00:01:18
    till the light bulb T passing through
  • 00:01:20
    the switch for the letter t
  • 00:01:22
    now let us look at the light bulb for
  • 00:01:24
    the letter e
  • 00:01:25
    as the key for letter e is pressed you
  • 00:01:28
    can see that the corresponding light
  • 00:01:30
    bulb for the letter e is cut off and
  • 00:01:32
    there is no way it can glow as long as
  • 00:01:34
    the switch for the letter e is pressed
  • 00:01:36
    this tells us that in an Enigma machine
  • 00:01:38
    no letter can be converted to itself
  • 00:01:41
    e cannot be converted to e t cannot be
  • 00:01:44
    converted to T and so on
  • 00:01:47
    this is the first weakness of the Enigma
  • 00:01:49
    machine which we will exploit to break
  • 00:01:51
    its code
  • 00:01:52
    let us say that we have intercepted the
  • 00:01:54
    following radio transmission
  • 00:01:57
    and since it is intercepted at 6am in
  • 00:01:59
    the morning we expect it to contain a
  • 00:02:01
    weather forecast something like this
  • 00:02:04
    weather is clear Heil Hitler is our
  • 00:02:06
    guess
  • 00:02:07
    the question that remains is how do we
  • 00:02:09
    match the letters between the
  • 00:02:11
    intercepted message and the guest
  • 00:02:12
    message
  • 00:02:13
    this is where we are going to exploit
  • 00:02:15
    the first weakness of enigma
  • 00:02:18
    let us align Our Guest message at the
  • 00:02:20
    very beginning of the intercepted
  • 00:02:21
    message
  • 00:02:23
    the very first pairing of letter implies
  • 00:02:25
    that w got encrypted to w
  • 00:02:28
    as we have seen no letter can be
  • 00:02:30
    converted to itself in enigma
  • 00:02:33
    so this alignment is not right
  • 00:02:36
    let us Slide the guest message by one
  • 00:02:38
    step
  • 00:02:39
    again we have letter A getting encrypted
  • 00:02:42
    to itself which cannot be right
  • 00:02:44
    sliding again
  • 00:02:46
    we have L and R matching
  • 00:02:49
    let us continue sliding till none of the
  • 00:02:51
    letter from intercepted message matches
  • 00:02:53
    with the corresponding letters from the
  • 00:02:55
    guest message
  • 00:03:01
    thank you
  • 00:03:04
    voila
  • 00:03:05
    we found a case where none of the
  • 00:03:07
    letters are getting converted to itself
  • 00:03:10
    this pairing between the intercepted
  • 00:03:12
    message and the guest message is also
  • 00:03:13
    called as a crib
  • 00:03:15
    so we have found a crib
  • 00:03:18
    just as a check we can slide further to
  • 00:03:20
    check whether we have one more Crib in
  • 00:03:21
    this case which is a possibility
  • 00:03:24
    [Music]
  • 00:03:27
    it looks like we have only one Crib in
  • 00:03:29
    this case
  • 00:03:30
    this makes things easier for us since we
  • 00:03:33
    now have a definite one-to-one
  • 00:03:34
    correspondence between the intercepted
  • 00:03:36
    and guest message
  • 00:03:38
    just as a side note this pairing is the
  • 00:03:41
    same one we had gotten in episode 1 and
  • 00:03:43
    2.
  • 00:03:44
    so we are effectively trying to break
  • 00:03:46
    the code from the encrypted messages
  • 00:03:48
    from episode 1 and 2.
  • 00:03:50
    and if we are successful we should get
  • 00:03:52
    the same settings as an output which
  • 00:03:54
    reuse back in those episodes
  • 00:03:57
    now that we have a crib let us try to
  • 00:03:59
    understand how the Bombay machine worked
  • 00:04:01
    to use that crib to crack the Enigma
  • 00:04:04
    recalling the flow of letters from
  • 00:04:06
    episode 2 the letter first goes through
  • 00:04:08
    the plug board
  • 00:04:10
    then through rotor 1 rotor 2 rotor 3
  • 00:04:13
    gets reflected on the rotor 3 then to
  • 00:04:15
    rotor 2 rotor 1 and back to the plug
  • 00:04:17
    board finally lights up the light bulb
  • 00:04:20
    among these series of conversions the
  • 00:04:22
    rotor 1 to rotor 1 conversions are only
  • 00:04:25
    dependent on rotor positions
  • 00:04:28
    in other words these conversions are
  • 00:04:30
    functions of the rotor position
  • 00:04:32
    let us assume that the initial rotor
  • 00:04:34
    position is X
  • 00:04:36
    this would be the setting that the
  • 00:04:38
    person using Enigma would have read in
  • 00:04:40
    the settings sheet
  • 00:04:41
    if you recall in Enigma machine the
  • 00:04:44
    rotor rotates every time a key is
  • 00:04:45
    pressed
  • 00:04:47
    so we can say that w converts2o at X
  • 00:04:50
    plus one
  • 00:04:51
    similarly e converts to T at X plus two
  • 00:04:54
    a converts to H at X plus 3 and so on
  • 00:04:58
    objective of the Bombay machine is to
  • 00:05:01
    find X and to find the plug board
  • 00:05:03
    settings
  • 00:05:04
    let us now see how Bombay machine was
  • 00:05:06
    designed to achieve these objectives
  • 00:05:08
    [Music]
  • 00:05:10
    to understand easily let us take a
  • 00:05:12
    simplified example of a crib
  • 00:05:14
    here a d d add is converted to c c a
  • 00:05:19
    let us also assume for the sake of
  • 00:05:21
    Simplicity that there are only six
  • 00:05:23
    alphabets in English language
  • 00:05:26
    a b c d e f
  • 00:05:31
    in the six letter World our 26-letter
  • 00:05:34
    Enigma machine shrinks to six letter
  • 00:05:36
    Enigma machine
  • 00:05:37
    [Music]
  • 00:05:40
    our crib conversion can be represented
  • 00:05:42
    by using three Enigma machines as shown
  • 00:05:44
    here
  • 00:05:45
    the only difference between these three
  • 00:05:47
    machines is the rotor positions
  • 00:05:50
    a converts to C at X plus one
  • 00:05:53
    D converts to C at X plus two
  • 00:05:57
    D converts to a at X plus 3
  • 00:06:00
    we need to find rotor position and plug
  • 00:06:02
    board settings where all of these
  • 00:06:04
    conversions happen one rotor position
  • 00:06:05
    away from each other
  • 00:06:07
    the most obvious way of finding the
  • 00:06:09
    Enigma settings is to take three Enigma
  • 00:06:11
    machines
  • 00:06:12
    set their rotor positions one position
  • 00:06:14
    away from each other and keep changing
  • 00:06:16
    the plug board settings and rotor
  • 00:06:18
    position until you get the conversion we
  • 00:06:20
    are looking for
  • 00:06:23
    this crude method of finding settings is
  • 00:06:25
    shown here
  • 00:06:27
    we have three Enigma machines
  • 00:06:29
    their rotor positions are just one step
  • 00:06:32
    away from each other
  • 00:06:33
    currently the setting under test is one
  • 00:06:36
    one one for the rotor position and ad
  • 00:06:38
    for the plug board
  • 00:06:40
    the three men operating these machines
  • 00:06:42
    are continually pressing the same letter
  • 00:06:44
    and are looking for a particular output
  • 00:06:46
    that is c c a respectively
  • 00:06:49
    in this case add is converting to e b c
  • 00:06:54
    so these settings are wrong
  • 00:06:57
    we have to try different setting
  • 00:06:58
    [Music]
  • 00:07:01
    here the output from the three enigmas
  • 00:07:04
    is c b e respectively
  • 00:07:06
    wrong again
  • 00:07:08
    moving on to the next setting
  • 00:07:11
    this one is for rotor position 1 4 2 and
  • 00:07:14
    plug board setting be
  • 00:07:16
    wrong again
  • 00:07:18
    moving on
  • 00:07:20
    let us check some random settings
  • 00:07:37
    at this rotor position 252 and plug
  • 00:07:40
    board setting a c we got to CCA as
  • 00:07:43
    output which is what we were looking for
  • 00:07:46
    so we have found the Enigma settings
  • 00:07:48
    that were used to convert a DD to CCA
  • 00:07:52
    this is a very crude and lengthy process
  • 00:07:54
    to try to crack the Enigma
  • 00:07:57
    in the real world with 26 letter Enigma
  • 00:07:59
    machines the number of possible settings
  • 00:08:01
    are so high that it would require more
  • 00:08:03
    than a lifetime to check all the
  • 00:08:05
    settings
  • 00:08:06
    Alan Turing wanted to build one machine
  • 00:08:08
    which can search for the right settings
  • 00:08:10
    on its own and in a much more efficient
  • 00:08:12
    way
  • 00:08:13
    the world will come to know that machine
  • 00:08:15
    as the Bombay machine
  • 00:08:18
    let us look at the design philosophy of
  • 00:08:20
    the Bombay machine
  • 00:08:22
    we will start with Bombay rotors
  • 00:08:25
    here are Enigma rotors
  • 00:08:27
    again they are from the six letter world
  • 00:08:30
    input is given to the yellow wires in
  • 00:08:33
    each rotor
  • 00:08:34
    output of each individual rotor is taken
  • 00:08:37
    from the blue wires
  • 00:08:38
    if you recall from the episode 1 rotor 2
  • 00:08:41
    rotates one step every time rotor 1
  • 00:08:43
    rotates one complete circle
  • 00:08:46
    rotor 3 rotates one step every time
  • 00:08:48
    rotor 2 rotates one complete circle
  • 00:08:51
    if we give voltage to the first wire
  • 00:08:53
    that is if we give a as input it goes
  • 00:08:55
    through all the rotors and back to give
  • 00:08:57
    output as B
  • 00:09:00
    the Bombay rotors are shown here
  • 00:09:03
    they are derived from the Enigma rotors
  • 00:09:06
    they essentially separate the return
  • 00:09:08
    path of the voltage and taking output
  • 00:09:10
    from separate set of wires
  • 00:09:12
    we have two identical rotor ones two
  • 00:09:14
    rotor twos and two rotor threes
  • 00:09:17
    again if we give a as input it goes
  • 00:09:20
    through all the rotors and back to give
  • 00:09:22
    output is B
  • 00:09:23
    only difference between the Enigma
  • 00:09:25
    rotors and Bombay rotors is that the
  • 00:09:27
    input and output corresponds to separate
  • 00:09:29
    set of wires
  • 00:09:31
    Bombay rotors and Enigma rotors are
  • 00:09:33
    electrical equivalent of each other
  • 00:09:36
    if Enigma rotors convert a into B then
  • 00:09:39
    so do the Bombay rotors
  • 00:09:41
    just for distinguishing the rotors in
  • 00:09:43
    the return path let us color them
  • 00:09:45
    differently
  • 00:09:47
    for the sake of Simplicity the six wires
  • 00:09:50
    can be represented with a single cable
  • 00:09:52
    as shown here
  • 00:09:54
    notice that since we have two identical
  • 00:09:56
    rotor ones they may as well be
  • 00:09:58
    physically mounted on the same
  • 00:09:59
    mechanical shaft
  • 00:10:01
    we have enlarged the rotors in the input
  • 00:10:03
    path
  • 00:10:05
    and now we can place The Identical
  • 00:10:07
    rotors on the same shaft
  • 00:10:11
    there you go
  • 00:10:18
    this is exactly what Bombay rotors look
  • 00:10:20
    like in the machine built by Alan Turing
  • 00:10:24
    [Music]
  • 00:10:25
    to reiterate the Bombay rotors and
  • 00:10:27
    Enigma rotors are electrical equivalent
  • 00:10:29
    of each other
  • 00:10:31
    if Enigma rotors convert a into B then
  • 00:10:33
    so do the Bombay rotors
  • 00:10:36
    now that we have learned about the
  • 00:10:37
    Bombay rotors let us introduce the
  • 00:10:39
    concept of equivalent rotor circuit
  • 00:10:42
    this concept is vital for explaining how
  • 00:10:44
    the Bombay machine works
  • 00:10:47
    let us take the Bombay rotors at the
  • 00:10:49
    position one one one
  • 00:10:51
    if we give a as input it goes through
  • 00:10:53
    all the rotors to give the output as B
  • 00:10:56
    so we can draw a line connecting A and B
  • 00:10:59
    in the equivalent rotor circuit for this
  • 00:11:01
    rotor position
  • 00:11:02
    if we give b as input it goes through
  • 00:11:05
    all the rotors to give the output as a
  • 00:11:08
    so we can draw a line connecting B to a
  • 00:11:10
    in the equivalent rotor circuit
  • 00:11:13
    if we give c as input it goes through
  • 00:11:15
    all the rotors to give the output as f
  • 00:11:18
    so we can draw a line connecting C to F
  • 00:11:21
    in the equivalent rotor circuit
  • 00:11:24
    and similarly we can complete the
  • 00:11:26
    equivalent circuit for the rest of the
  • 00:11:28
    letters
  • 00:11:30
    [Music]
  • 00:11:33
    the rotor equivalent circuit is
  • 00:11:35
    electrically equivalent to the rotors
  • 00:11:38
    if the rotors convert f into C the
  • 00:11:40
    equivalent rotor circuit will also
  • 00:11:42
    convert f into C at that rotor position
  • 00:11:48
    let us Advance the rotors by one
  • 00:11:50
    position
  • 00:11:51
    the equivalent rotor circuit is
  • 00:11:53
    completely changed
  • 00:11:55
    this should be obvious because of the
  • 00:11:57
    fact that the electrical connections of
  • 00:11:59
    the rotors change as the rotor position
  • 00:12:01
    changes
  • 00:12:02
    [Music]
  • 00:12:04
    now let us build the electrical circuit
  • 00:12:07
    for the Bombay machine
  • 00:12:09
    if you recall from earlier part of this
  • 00:12:11
    video input letter goes through these
  • 00:12:13
    sequence of conversions before the
  • 00:12:15
    output is generated by the Enigma
  • 00:12:16
    machine
  • 00:12:18
    the rotor conversions in this diagram
  • 00:12:20
    can be replaced by the Bombay rotors as
  • 00:12:22
    shown here
  • 00:12:28
    now for the plug board there are six
  • 00:12:30
    possible connections
  • 00:12:32
    if a is not connected to any other
  • 00:12:34
    letter on the bloodboard the input will
  • 00:12:36
    directly go to the first wire of the
  • 00:12:38
    rotors corresponding to the letter A
  • 00:12:41
    if a is connected to be on the plug
  • 00:12:43
    board the input a will get converted to
  • 00:12:45
    B and it will connect to the second wire
  • 00:12:47
    of the rotors corresponding to the
  • 00:12:49
    letter b
  • 00:12:50
    similarly the rest of the possibilities
  • 00:12:53
    are shown
  • 00:12:54
    we need to find which one of these
  • 00:12:56
    possibilities is actually true
  • 00:12:58
    but for now all are equally probable
  • 00:13:02
    so we will keep all the wires as a
  • 00:13:04
    representation of the plug board
  • 00:13:07
    each of the wire here is a hypothesis or
  • 00:13:09
    a guess stating to which letter does the
  • 00:13:11
    letter A connects to on the plug board
  • 00:13:14
    only one of these hypotheses can be true
  • 00:13:16
    since you cannot possibly connect a to
  • 00:13:19
    multiple letters on the plug Board of
  • 00:13:20
    the Enigma machine
  • 00:13:24
    similarly we can represent six
  • 00:13:26
    hypothesis wires for the letter c
  • 00:13:32
    now let us replace the rotors with its
  • 00:13:34
    equivalent circuit for this rotor
  • 00:13:36
    position
  • 00:13:43
    this circuit is for conversion from a to
  • 00:13:45
    c
  • 00:13:47
    we can draw similar circuits for the
  • 00:13:49
    rest of the crib
  • 00:13:50
    let x equals one six two be the rotor
  • 00:13:53
    position Bombay machine is trying out as
  • 00:13:55
    a possible solution
  • 00:13:57
    these are the three circuits we have
  • 00:13:59
    made based on the crib
  • 00:14:01
    the rotors in these conversions are
  • 00:14:03
    placed one position away from each other
  • 00:14:04
    at X Plus One X plus two and X Plus 3.
  • 00:14:09
    notice that the rotor equivalent
  • 00:14:11
    circuits are different for each
  • 00:14:12
    conversion
  • 00:14:14
    this is expected as the equivalent rotor
  • 00:14:16
    circuit changes as the rotor position
  • 00:14:18
    changes
  • 00:14:20
    are these circuits connected to each
  • 00:14:22
    other
  • 00:14:23
    If You observe there are some common
  • 00:14:25
    cables
  • 00:14:26
    cable D is common between the second and
  • 00:14:29
    the third circuit
  • 00:14:30
    cable C is common between the first and
  • 00:14:33
    the second circuit
  • 00:14:35
    and cable a is common between the first
  • 00:14:37
    and the third circuit
  • 00:14:39
    rearranging these circuit connections we
  • 00:14:42
    get the circuit
  • 00:14:44
    this is what circuit looked like inside
  • 00:14:45
    the Bombay machine
  • 00:14:47
    it is intriguing isn't it
  • 00:15:00
    to check whether the current position x
  • 00:15:02
    equals 1 6 2 is the correct solution or
  • 00:15:05
    not we apply voltage to one of the wires
  • 00:15:08
    this voltage spreads to the all the
  • 00:15:10
    connected wires
  • 00:15:28
    in this case the voltage spread out to
  • 00:15:30
    all the wires in all the cables
  • 00:15:33
    if you look at cable C all the six wires
  • 00:15:35
    have the voltage
  • 00:15:37
    remember how we said that each wire is
  • 00:15:39
    in hypothesis of where the letter c is
  • 00:15:42
    connected to on the plug board
  • 00:15:44
    and only one of these hypotheses can be
  • 00:15:46
    true
  • 00:15:47
    however here since all the wires have
  • 00:15:50
    the voltage it is indicating that all
  • 00:15:52
    the hypotheses are true
  • 00:15:54
    this is definitely not possible
  • 00:15:57
    so we do not have a solution at this
  • 00:15:59
    rotor position x equals one six two as a
  • 00:16:03
    general rule if all the wires in the
  • 00:16:04
    cable set are showing voltage then we do
  • 00:16:07
    not have a solution and we need to try
  • 00:16:08
    the next rotor position
  • 00:16:09
    [Music]
  • 00:16:13
    in one go this Bombay circuit has
  • 00:16:15
    eliminated rotor position 162 as a
  • 00:16:18
    possible solution
  • 00:16:19
    doing this manually would have required
  • 00:16:22
    to check all the possible plug board
  • 00:16:23
    settings at rotor position 162.
  • 00:16:26
    this is why Bombay is much faster
  • 00:16:29
    [Music]
  • 00:16:31
    let us move to another rotor position x
  • 00:16:33
    equals two five two
  • 00:16:35
    notice that at this rotor position x
  • 00:16:38
    equals 2 5 2 the rotor equivalent
  • 00:16:40
    circuits have all been changed
  • 00:16:44
    now let us apply voltage to one of the
  • 00:16:46
    wires
  • 00:16:48
    in this case the voltage did not spread
  • 00:16:50
    to all the wires
  • 00:16:52
    we have one wire in each cable which
  • 00:16:54
    carries the voltage
  • 00:16:56
    so we have found a solution
  • 00:16:59
    if we look at cable C hypothesis that
  • 00:17:01
    letter C is connected to a is found to
  • 00:17:04
    be true since the first wire has the
  • 00:17:06
    voltage
  • 00:17:07
    the solution wire has isolated itself
  • 00:17:09
    from the rest of the bunch
  • 00:17:11
    Bombay has identified the solution for
  • 00:17:13
    the rotor position as x equals 2 5 2.
  • 00:17:17
    and the determined bloodboard settings
  • 00:17:19
    are C is connected to a a is connected
  • 00:17:22
    to C and D is not connected to any other
  • 00:17:25
    letter on the plug board
  • 00:17:26
    this is where the Bombay machine would
  • 00:17:28
    stop spinning and checking for further
  • 00:17:30
    rotor positions
  • 00:17:32
    this is the philosophy and the
  • 00:17:34
    underlining principle of working of the
  • 00:17:36
    Bombay machine
  • 00:17:42
    this is the crib we just used to break
  • 00:17:44
    the enigma's code
  • 00:17:46
    this is a special crib
  • 00:17:48
    it can be rearranged to form a loop
  • 00:17:56
    if you recall from episode 1 same Enigma
  • 00:17:59
    machine is used for encryption and
  • 00:18:01
    decryption
  • 00:18:02
    so if a converts to C for a particular
  • 00:18:05
    rotor position C also converts to a for
  • 00:18:08
    the same rotor position
  • 00:18:10
    this is actually the weakness number two
  • 00:18:12
    of the Enigma machine that we just
  • 00:18:13
    exploited to break its code
  • 00:18:16
    because of this weakness we can form a
  • 00:18:18
    loop like the one shown here and build a
  • 00:18:20
    circuit corresponding to this Loop
  • 00:18:22
    for Bombay machine to work we need to
  • 00:18:24
    find Loops in the crib like the one we
  • 00:18:26
    have here
  • 00:18:29
    only Loops are useful in Breaking the
  • 00:18:31
    Enigma with the Bombay machine
  • 00:18:35
    in summary cracking the Enigma with
  • 00:18:37
    Bombay machine involves three steps
  • 00:18:40
    first is to identify Loops in the given
  • 00:18:43
    crib
  • 00:18:44
    second is to connect the Bombay rotors
  • 00:18:46
    as per the loops
  • 00:18:48
    third step is to apply voltage to one of
  • 00:18:51
    the wires in the loop and run the rotors
  • 00:18:53
    until an isolated wire is found
  • 00:18:55
    in the next video we will take a look at
  • 00:18:58
    the full-size Bombay machine that we
  • 00:18:59
    have built and see it working as for the
  • 00:19:01
    principles developed in this video
  • 00:19:04
    if you think you have got some value
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    from this video do hit the Subscribe
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    see you in the next video
  • 00:19:15
    foreign
タグ
  • Enigma
  • Bombay Machine
  • Alan Turing
  • Cribbing
  • Codebreaking
  • Bletchley Park
  • Mathematics
  • Rotor Position
  • Plugboard Settings
  • World War II