Elementary Cyptography
Consider the steps involved in sending messages from a sender , S , to a recipient , R . –If S entrusts the message to T , who then delivers it to R , T then becomes the transmission medium . –If an outsider, O , wants to access the message (to read, change, or even destroy it), we call O an interceptor or intruder . Any time after S transmits it via T , the message is vulnerable to exploitation, O might try to access the message in any of the following ways: – Block it, by preventing its reaching R, thereby affecting the availability of the message. – Intercept it, by reading or listening to the message, thereby affecting the confidentiality of the message. – Modify it, by seizing the message and changing it in some way, affecting the message's integrity. – Fabricate the authentic-looking message, arranging for it to be delivered as if it came from S, thereby also affecting the integrity of the message. As you can see, a message's vulnerability refle...
