Cyber Security Chapter-4 (A)

What happens your data whe it is encrypted?

• It transferred to a third party,encoded sent back
• It is recorded to retain privacy from third parties
• It is compressed archieved and renamed.
• none

By encryption of a text we mean

• compress it
• expand it
• scrambling it to preserve its security
• hashing it

Certification of digital signature by an independant authority is needed because

• the authority checks and assures customer
• it is safe
• it gives confidence to business
• private key

DES works by using

• only permutation on 128 bits
• permutation and sustitution on 64 bits blocks of plain text
• 4 rounds of sustitution
• exclusive OR

Encryption can be done

• only on textual data
• only on ascii coded data
• on any bit string
• only on mnemonis data

By symmetric key encryption we mean

• only public keys are used for encryption
• private and public keys are used for encryption
• one private key used for both encryption and decryption
• hashing

A digital signature is required to

• prove that the message was sent by the sender
• deliver proper message
• prove validity
• none

The responsibilities of a certificate authorities for digital signature is to authenticate the ________

• public keys of subscribers
• hash function used
• private keys of subscribers
• key used in DES

Hashed message is signed by a sender using

• his private key
• his public key
• receivers public key
• symmetric key

public key system is useful because

• there is no key distribution problem
• faster
• compressed message
• hashing the message