#network security

Question

1. What is the difference  between message integrity  and message  authentication ?

I have read in frozen :

message   integrity -:  message  digest (generated by applying  hash function on message ) is being added with original message  and by verification of this digest(creating the digest by received message ) on the recipient end it will be accepted.

Message authentication :we generate message authentication  code (MDC)(  by using symmetric key and hash function )and that will be added with original message , and it will be sent . On the recipient  end it will be accepted  by verifying the MAC.  

So now my doubt is .... by both of the procedure  we r doing the same in both we are verifying digest in both for assurance of not modified data.

 Explain  it pls.  I m not able to visualise it .

Thanks

Answer 1

Message integrity

Message integrity is provide via Hash  function. The hashing function is used are 1 way Hash function  which means given a data it will produce a unique hash for it.. 

Receiver on getting the message+sign ,calculate the hash of the message using the same 1 way hashing function once used by the sender. Then it compare the computed hash with hash it obtained from the decrypted digital signature. If both hash matches , it means that data is not changed during the transmission or message is same as what sender has sent.

Message Authentication

Message authentication is provide by the use of asymmetric keys.

Sender sign the message digest using it private key and send this as digital signature along with the message.On receiving , Receiver will then try to decrypt this message digest (signature ) using the public key of the sender. If it can decrypt the message digest using the sender public key , then it can know for sure that the message was sent by the sender only as he only can have his private key that was once used to encrypt it   .

Now your doubt,

in diagrams  you find in book for either of these will have same parts, but what is important to note here is that the message hashing is for checking integrity check and encrypting or decrypting  the message digest  is for authentication .

Hope i cleared your doubt.