Explain a scenario which shows OTP is malleable Explain how we can break Content

Question

Explain a scenario which shows OTP is malleable Explain how we can break Content Scramble System (CSS) which is widely used in encrypting DVD file systems. 03-Block Cipher.pptx What is a block cipher? (show me the schematic view of block cipher including E,D algorthm.) (slide 3) How DES algorithm works? Please show the Encryption and Decryption schematic view What do S-boxes do in DES algorithm? Why can't we use double DES? (what is its time complexity) slide 34-35 Different attacks on Block cipher alg.? slide 40 How AES alg. works? Schematic view and explanation. What's wrong with Electron Cod Book? slide 96

Explanation / Answer

EXPLAIN A SCENARIO WHICH SHOWS OTP IS MALLEABLE

OTP stands for One time pad. It is an encryption technique which makes the use a pre shared key which is exactly the same length as the message to be transferred. The plain text or the message is paired with the one time pad or the pre shared key. Encryption is done by combinig pne bit of the plain text message with one bit of the key using modular addition. However this encryption is not authentic and is malleable.

If the attacker knows the plain text and the encypted text he can easily the deciper the corresponding one time pad value and can modify and send the message to the receiver. In this encryption technique the receiver has no means of verifying whether he has recieved the correct message or not. Thus this ecryption algorithm is malleable.

EXPLAIN HOW WE CAN BREAK CONTENT SCRAMBLE SYSTEM (CSS) WHICH IS WIDELY USED IN ENCRYPTING DVD FILE SYSTEMS

Content Scramble System is an encrption technique which is also called as DRM(Digital Rights Management) method used to ecnrpt DVDS to prevent them from being copied. It provides copyright to the DVD to prevent its piracy. The CSS uses a cryptographic key of size 40 bits which makes it vulnerable to many attacks. These days many softwares are avaliable which remove the encrption from the DVDs and help to copy the contents.One such example of the software is DVDSmith. This software helps taking the backup of the contents of the DVD.

Given are the steps to be done once we have installed the software:

Thus these are the steps to break down the CSS

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