3.1 : Message encryption, message authentication code, hash

function

3.2 : An authenticator that is a cryptographic work of both the

information to be authenticated and a mystery key.

3.3: A, A hash code is computed from the source message, scrambled

utilizing symmetric encryption and a mystery key (B), This is the same method

as in (a) but that public-key encryption is utilized; the sender scrambles the

hash code with the sender’s private key, and the recipient decodes the hash

code with the sender’s open key. (c) A mystery esteem is added to a message and

at that point a hash code is calculated utilizing the message additionally

mystery esteem as input. At that point the message (without the mystery esteem)

and the hash code are transmitted

3.4: a – H can be connected to a square of information of any

measure.

b- For any given esteem h, it is computationally infeasible to

discover x such that H(x) = h. This is some of the time alluded to in the

writing as the one-way property.

c- It is computationally

infeasible to discover any combine (x, y) such that H(x) = H(y).

3.5 : The

compression work is the essential module, or fundamental building piece, of a

hash work. The hash work comprises of iterated application of the compression

work.

3.6: Plaintext, Encryption algorithm, Public and private keys,

Ciphertext, Decryption algorithm

3.7 : a – Encryption/decryption: The sender scrambles a message

with the recipient’s open key

b- Digital signature: The sender “signs” a message with

its private key. Marking is accomplished by a cryptographic calculation

connected to the message or to a little piece of information that is a work of

the message.

c- Key exchange: Two sides participate to trade a session key. A

few diverse approaches are conceivable, including the private key(s) of one or

both parties.

3.8: The key utilized in ordinary encryption is regularly alluded

to as a mystery key. The two keys utilized for public-key encryption are

alluded to as the open key and the private key.

3.9: digital signature: is an verification instrument that empowers

the maker of a message to join a code that acts as a signature. The signature

is shaped by taking the hash of the message and scrambling the message with the

creator’s private key. The signature ensures the source and astuteness of the

message.