Question

NC3A-

• 3.1 List three approaches to message authentication.

• 3.2 What is a message authentication code?

• 3.4 What properties must a hash function have to be useful for message authentication?

• 3.5 In the context of a hash function, what is a compression function

Answer 1

Answer)

3.1) The message authentication is mostly being achieved by the use of Message Authentication Code (MACs), the authenticated encryption (AE) and the Digital Signatures.

The message authentication code is referred to as the digital authenticator which is being used as the integrity check with respect to the secret key being shared by the 2 parties for authenticating the information being transmitted between those.

This is being based on the use of a cryptographic hash or symmetric encryption algorithm. Here the authentication key is being shared with a minimum of 2 parties or 2 communication devices whereas it will fall in the existence of the third party as the algorithm would no longer be effective in detecting the forgeries. Also, the key would also be randomly be generated for avoiding the recovery via the brute force searches as well as related key attacks meant for identifying from that of the messages transmitting the medium.

3.2) When cryptography is taken into consideration the message authentication code is referred to as tag and is a short piece of information which is being used for authenticating the message. It helps in confirming the message is generated from the stated sender and also has not changed.

3.4) Hash function has certain properties which make the message authentication cryptographically secure. This takes input as a message of an arbitrary length and then produces the message digest or the hash of the fixed length.

The hash function uses the input data and also the hash function uniformly distributed the data via the complete set of possible hash values.

3.5) When cryptography is considered the compression function is referred to as the function which would transform the two fixed-length which is at a fixed-length output.

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