Explain the following concepts: What is your understanding of the difference bet
ID: 3752046 • Letter: E
Question
Explain the following concepts:
What is your understanding of the difference between a stream cipher and a block cipher?
What are two ways to launch a cryptanalytic attack against a cipher (based upon what the attacker knows or has in possession)? Be sure to provide detailed examples.
What is your understanding of the difference between an unconditionally secure cipher and a computationally secure cipher?
Your organization has asked for a cryptographic algorithm recommendation for a new project that requires high-level security. What algorithm would you recommend and why?
Explanation / Answer
a) Difference between stream cipher and a block cipher.
Context
Steam Cipher
Block Cipher
BASIC
Stream cipher basically encrypt by taking unit byte of plain text or message
Block cipher basically divides the message or text into blocks And then encrypt it
NO BITS
At a time 8 bit is converted.
At a time 64 or 128 bits of block can be converted
REVERSE ENCRYPTION
Reversing the encrypted text is easy as it uses XOR to encrypt.
Reversing the encrypted text is
difficult
KEY
It uses different keys for different bits.
It uses same key for encrypting different blocks
b) Cryptanalysis is the technique s of encode and decode secret messages. In the cryptanalytic attack
the encrypted text is recovered without having the key. It certainly possible if the attacker have complete knowledge of encryption algorithm
Here is some types of well known cryptanalytic attacks1.
1.Cipher text only attack
-In this attack cipher text is there and the attackers goal is just to find the plain text of
respective ciphered text or better to find the key used.
2.known plain text attack
-Here both cipher text and plain text of corresponding messages are given his task is to find out the key only
3.chosen plain text attack
-Here both plain and ciphered text is known ,but the attackers can choose plain text that gets encrypted, using this he has to find key or the algorithm that is used to encrypt in next plain text
c) An unconditional secure scheme of encryption means ,if the cipher text generated by the scheme that does not contain enough information to determine the corresponding plain text ,no matter how many cipher text is available.
An encryption scheme is called computationally secure if 1.The cost of breaking the cipher exceeds the value of encrypted information, Or 2. The time required to break the cipher exceeds the useful ness lifetime of that information.
d) As per my research AES(Advance encryption standard) encryption algorithm should be used if you want a high security of your data.
It is one of the mostly used cipher for data encryption. Us government also using it protect its classified data.
Features of AES:
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Context
Steam Cipher
Block Cipher
BASIC
Stream cipher basically encrypt by taking unit byte of plain text or message
Block cipher basically divides the message or text into blocks And then encrypt it
NO BITS
At a time 8 bit is converted.
At a time 64 or 128 bits of block can be converted
REVERSE ENCRYPTION
Reversing the encrypted text is easy as it uses XOR to encrypt.
Reversing the encrypted text is
difficult
KEY
It uses different keys for different bits.
It uses same key for encrypting different blocks
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