Cyber reason for mac mac#
MAC technique does not provide a non-repudiation service. Non-repudiation is the assurance that a message originator cannot deny any previously sent messages and commitments or actions. This requires establishment of shared secret prior to use of MAC. It can provide message authentication among pre-decided legitimate users who have shared key. There are two major limitations of MAC, both due to its symmetric nature of operation − As a bottom-line, a receiver safely assumes that the message is not the genuine. If the computed MAC does not match the MAC sent by the sender, the receiver cannot determine whether it is the message that has been altered or it is the origin that has been falsified. If they match, then the receiver accepts the message and assures himself that the message has been sent by the intended sender. The receiver now checks equality of freshly computed MAC with the MAC received from the sender. On receipt of the message and the MAC, the receiver feeds the received message and the shared secret key K into the MAC algorithm and re-computes the MAC value. If confidentiality is required then the message needs encryption. Here, we assume that the message is sent in the clear, as we are concerned of providing message origin authentication, not confidentiality. The sender forwards the message along with the MAC. The major difference between hash and MAC is that MAC uses secret key during the compression. Similar to hash, MAC function also compresses an arbitrary long input into a fixed length output. The sender uses some publicly known MAC algorithm, inputs the message and the secret key K and produces a MAC value.
Let us now try to understand the entire process in detail − The process of using MAC for authentication is depicted in the following illustration − For establishing MAC process, the sender and receiver share a symmetric key K.Įssentially, a MAC is an encrypted checksum generated on the underlying message that is sent along with a message to ensure message authentication. MAC algorithm is a symmetric key cryptographic technique to provide message authentication.
Message authentication can be provided using the cryptographic techniques that use secret keys as done in case of encryption. In this threat, the user is not sure about the originator of the message. In the last chapter, we discussed the data integrity threats and the use of hashing technique to detect if any modification attacks have taken place on the data.Īnother type of threat that exist for data is the lack of message authentication.
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