I am new to Cryptography and unable to understand clearly about MAC concept. As per MAC concept, Sender 'A' will encrypt the original message with symmetric key to create MAC1 value and then will send the original message and MAC1 value to the receiver 'B'. Now, 'B' will encrypt the original message with same symmetric key to create MAC2 value.
If MAC1=MAC2, then message integrity is achieved.
I just want to understand why do the sender send original text in plain format? This would also attract eavesdrops to capture the message?
Please correct me if my understanding in wrong.