a)    Define the type of security attack in each of following cases, either passive or active and why?

         i.           A student breaks into a professor's office to obtain a copy of the next day's test.

       ii.           A student gives a check for $10 to buy a used book. Later he finds that the check was cashed for $100.

b)   How internal wiring of Rotor Machine effects the encryption? Explain with the help of example

 

a) (Please refer to the explanation below for the detailed description of why the situation is active or passive)

i. Passive Attack

ii. Active Attack

b) Enigma machine is an encryption device used by Germans during World War II, mostly for military communication. It uses a rotor mechanism to scramble the 26 letters of the alphabet. Each time a keystroke is entered, the rotor will be rotating with a gear.

Step-by-step explanation

a)

i. Passive Attack - focuses on copying of messages (remains unchanged)

A passive attack is the kind of attack where an attacker observes the messages and copies it. With this kind of attack, confidentiality is the one most vulnerable. So in this case, the student was able to obtain a copy of tomorrow's exam by breaking in the professor's office. The test remains unchanged because the student just grabbed a copy, but still this copy must not be accessed and must be kept confidential. It is a security breach where confidentiality was compromised.

ii. Active Attack - focuses on modification of messages

In this situation, we can obviously observe that there was a change or modification with the data. From the initial $10 written, it became $100, and this is probably done by the attacker. An active attack is the kind of attack where the attacker tries to modify or change the message. In this case, integrity of the data is the one most compromised.

b) Rotor machines are mechanical devices than can be used for encryption algorithms. The basic operation of this machine applies with a typewriter style which contains characters, usually of 26 characters (alphabet). The user will input a character or text, and it will output a different one. With the use of rotors, the encryption becomes more complex than ciphers. This rotor (or these rotors), will have an internal wiring. Each time a keystroke is entered, the rotor will be rotating with a gear. And since this is a machine used for encryption, the certain internal wiring of the rotor is kept confidential.

For an example, in a normal substitution cipher, if we enter two same keystrokes like BB, then it will be HH - where B is always H. Now using a rotor (depending on the internal wiring), for the sake of understanding by example, if we enter BB, it will be HI. The second output keystroke is obviously different, thus making it more complex than cipher.

A good example that I found of a rotor machine is the Enigma machine. An Enigma machine is an encryption device used by Germans during World War II, mostly for military communication. It uses a rotor mechanism to scramble the 26 letters of the alphabet. Adding a rotor machine in between the keyboard and the lamp board jumbles the letters for encryption because of the internal wiring of the rotor. So for example, pressing B will produce a different output letter other than B. Every time a key is pressed, the rotor will be rotating one step further. So in this case, if you press B again, it will be a different output compared to the latter. The steps or rotations of the rotor will be depending on your characters in the machine. So, for 26 letters, there will be 26 steps before a full rotation. Rotors can be added to the machine and doing this will surely improve the security of the encryption. Enigma machines most likely contain three to four rotors.