Decrypt enigma cipher

The Enigma is one of the better known historical encryption machines, and it actually refers to a range of similar cipher machines. The first Enigma machine was invented by a German engineer named Arthur Scherbius at the end of the first world war. If you would like to encrypt some of your own Enigma messages, have a look at the javascript example.

This section will talk about the Enigma I aka Wehrmacht Enigma, other variants are similar in operation. The 'key' for the enigma consists of several elements:.

For information on the procedures used by the Germans during WW2 when sending Engima messages, including how the indicators were set, see this description.

We will assume for now that as the letter 'A' is enciphered each rotor is in its start position 'AAA'. Each rotor applies a simple substitution operation. The substitution table for rotor III can be seen below. B is replaced with D, C is replaced with F etc. So after the letter 'A' goes through the rotor, it comes out as a 'B'. The letter 'B' is now input through rotor II, where it is replaced by 'J' etc.

This is best depicted using a table for a full description of the rotor wirings for each rotor, see this wikipedia page :. After coming out of the reflector, the letter is sent back through the rotors in the reverse direction this means the inverse substitution is applied. We can see from the table that after the enciphered letter comes back out rotor III at the end, we are left with the letter U.

However, the brilliant and intuitive Rejewski made the stunningly guess that the Germans, obsessed with efficiency and order, would place the keys alphabetically. After Hitler invaded Poland, Cipher Bureau passed on their successful codebreaking work and cipher technology to Britain.

Right before Poland was overrun by the German blitzkrieg, their cryptologists led the way to hacking the Nazis. GateKeeper Sales For pre-sale questions or info. Contact Sales. See GateKeeper proximity access control in action. View our Live Demo! Pin It on Pinterest. Therefore the same machine can be used for encoding and decoding without any rewiring necessary [1]. The message is typed in like on a typewriter.

Each time a key is hit, current flows through the contacts in the scrambler unit and illuminates a lamp with the enciphered letter showing. Little notches on the rotor's sides take care of that. To decrypt a message, one needs not only an Enigma machine, but also the knowledge of the starting state, i. To decrypt the message, the machine must be set to the same starting state, and the cipher text is entered.

Output is the plain text. To enhance the security of Enigma, five rotors with different internal wirings were in use. Any three of these could be used in the machine in any order. The rotors had letters on their outer rim. This rim was moveable, giving the ring positions. Basically, the rings allow shifting the relative position of letters shown to internal core wiring of the rotor.

Exactly the same position of the wheel can now show a different letter. A further gain of security is added by implementing the so called Steckerboard. Before the letters get to the scrambler unit, they may be swapped by cross-connecting them. Connecting A with say E by a plug swaps A with E and vice versa.

Using a number of plugs around 5 or 6 maximun 13 raises the possible states by a factor of billion. With the methods given at these days, i. This led the German officials to the claim that their codes were unbreakable and safe [6]. To summarize, Enigma's security relies on the rotor settings, the ring settings, and the Steckerboard connections.

For completeness, the following image shows a real Enigma. Slightly different Enigmas were in use. The German Navy used a somewhat more sophisticated model then the Army. A model with four rotors was developed, features to enhance security were added during the life of Enigma, and the way how to use it was altered frequently [1].

Some basic guidlines and features stayed mostly the same though. The basic settings were written down in a code book, and changed daily. Basic settings are the rotors in use and their arrangement, the ring settings, and the Stecker connections. The user picked a random starting position for the wheels. It was transmitted as part of the message. Messages had a header consisting of sender, time, date and a code for recipient. Possible recipients were Army, Navy etc.

Using codes made clear if a message needed to be decoded by the interceptor at all, i. The header was transmitted en clair. The sender then picked another random starting position for the wheels, encoded it, and included it twice after the message header. Therefore the two triples of letters after the header gave the recipient, when decoded according to the code book, the actual position of the wheels to which Enigma needed to be set for decoding the text.

After that, the message body was appended. Messages were supposed to be shorter than characters. The longer a message, the more likely it was for it to be broken. If needed, messages were split into pieces.

Each piece was then encoded with a different key. There were certain conventions how to separate parts, words, make paragraphs and so on. Words were separated with X. Numbers had to be spelled out and so forth [6]. Decoding of a message made necessary the possession of an Enigma machine, the starting state, and the knowledge of how to use the machine.

Breaking the Code:. With all its perfection, especially for the time, there were also flaws in Enigma. The human factor, and not to underestimate the belief in its being unbreakable eventually led to the code being cracked.

Untrained and lazy radio staff used bad keys like keyboard diagonals and abbreviated swear words [6]. The whole concept of transmission with the doubly encoded starting position of the rotors had weak points. Knowing this gave the code breakers an entry point into Enigma's big secret.

Knowing parts of a message in plain text and cipher text was called a crib. Cribs are starting points for the attack on breaking the codes. First and successful attempts at Enigma were being done by the Poles. In , when suddenly those messages became no longer understandable, it was clear that Germany had started to employ some ciphering scheme [6].

There is some myth aroud how Poland found out about what was behind these codes. It was likely a combination of espionage and simply luck how they found out about the electro-mechanical ciphering machine Enigma. It is said that some factory workers and even money needing German officials sold their knowledge.

Another incident might be when Germany sent an Enigma accidentally by regular mail, and the Polish secret service had time over a weekend to inspect the machine. It is however without a doubt majorly the achievement of a number of talented young Polish mathematicians to aquire the deeper knowledge on how to use Enigma [5].

The commercial Enigma was not of too much help, but gave some clues on how the machine supposedly worked. Poland may have bought some messages in plain text and cipher text, but they knew little about the rotor wiring at first, and without starting keys, no message could be deciphered. The mathematician Rejevski came up with a method to find the rotor wiring using linear algebra. All these little clues together gave them enough knowledge to build models of Enigma, and finally a replica.

Furthermore, knowing that the first six letters were two equal triples of letters when decrypted helped him develop a scheme, that when analyzing many messages of the same day allowed coming up with the initial settings.