Overview Of Network Security And Cryptography Computer Science
This doesn't solve the problem because the hash function is known and can be used by an intruder who is interested with the message being transmitted by calculating a new hash and appending it to the message. Since the hash function is clearly known the message my be rendered insecure by not applying keyed hash- in which case the hash key is combined with the secret key.
In symmetric algorithm, identical key (symmetric key) is applied both data encryption and data decryption. One of the bases is that symmetric key must be kept secret at all times by both the sender and recipient who are utilizing encrypted communications. In case an attacker discovers the symmetric key, integrity and authentication of data is compromised. Hence, the attacker is capable of disguising him/her -self as the genuine sender. If Alice authenticated the message by computing a MAC based on a key she shares with Bob, Bob knows Alice really placed the order because nobody other than Bob and Alice know that key. If Bob knows he didn't create the message he knows it must have been Alice. But he can't prove it to anyone! Because Bob knows the secret used by Alice, he may have forged the key used on the message and besides, Bob is not in a position to convince the judge that he did not commit the crime. On the other hand, incase a public key was used; Bob the court of law can prove that message was certified with Alice's key. Alice can however argue that an intruder stole her key and disguised as herself although the contract between her and Bob could qualify for damages for failure of protecting the key.
The original binary string
Is divided into two (2) 32 bit binary string
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