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Message Authentication Code (MAC): Definition and Use in EFTs

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Updated June 29, 2023

A message authentication code (MAC), or tag, is a security code that is typed in by the user of a computer to access accounts or portals. This code is attached to the message or requ🌌est sent by the user. MACs attached to the message must be recognized by the receiving system in order to grant the user access.

Key Takeaways

Message authentication codes (MACs) are a security measure commonly attached to electronic financial transactions.
Codes are generated randomly by algorithms.
MACs help ensure that messages can be sent only once.
In the communications industry, MAC also stands for media access control, so the term message integrity code (MIC) is used instead.

♔ Understanding Message Authentication Codes (MACs)

MACs are commonly used in electronic funds transfers (EFTs) to maintain information integrity. They confirm that a message is authentic, really does come from the stated sender, and hasn’t undergone any changes en route. A verifier who also possesses the key can use it to identify changes to the content of the message in question.

Note

MACs usually are required to access any kind of financial account. Banks, 澳洲幸运5官方开奖结果体彩网:brokerage firms, trust companies, and꧋ any other deposit, investment, or insurance company that offers online access can employ these codes. They are a vital component of financial cryptography.

Algorithms Used to Generate MACs

Three algorithms typically comprise a MAC: a key generation algorithm, a signing algorithm, and a verifying algorithm. The key generation algorithm chooses a key at random. The signing algorithm sends a tag when given the key and the message. The verifying algorithm is used to verify the authenticity of the message when given the key and tag; it will return a message of accepted if the message and tag are authentic and unaltered, but otherwise, it will return a message of rejected.

Warning

The message should contain some data that ensures that it can be sent only once. For example, a one-time MAC, timestamp, or sequence number could guarantee 🌄that the message can be sent only once. Otherwise, the system could be vulnerable to a replay attack, in which an attacker intercepts the message after it has been decoded and retransmits it at a later time, replicating the original results and infiltrating the system.

For example, the sender sends a message, such as an EFT, through the MAC algorithm, which generates a key and attaches a MAC data tag to the message. The recipient gets the message, runs it back through the MAC algorithm with the same key, and gets a second data tag. They will then compare this MAC data tag with the first one attached to the message when it was transmitted. If the code is the same at both ends, the recipient can safely assume that the message's data integrity is intact. If not, however, it means that the message was altered, tampered with, or forged.

Message Integrity Codes (MICs)

Sometimes, the term message integrity code (MIC) will be used instead of MAC. This is most often done in the communications industry, where MAC traditionally means media access control address (MAC address). However, MIC also can be used to refer to message digest, which does not use secret keys in the same manner as a MAC, and cannot offer the 💛same level of security without further encryption.

Frequently Asked Questions

What Is the Difference Between a Message Authentication Code (MAC) and a Digital Signature?

With MACs, the same key is used by both sides of a message—the sender and the recipient. 🦋This is so the recipient can verify the message has not been altered or otherwise interfered with en route. A digital signature serves only as verification that a message was sent by the owner of the digital signature.

What Is the Alternate Name for a Message Authentication Code (MAC)?

MACs also are commonly called tags. They are a type of cryptographic checksum and may be referred to as such. Cryptographic checksums use cryptographic algorithms to assign matching data to both ends of a message for verification purposes.

What Is a Message Authentication Code (MAC) Used For?

MACs can be used any t𓂃ime it is necessary to insure that a message has not been altered or otherwise tampered with in transit to the recipient. They commonly are used for electronic funds transfers (EFTs), but they are not unique to that type of transaction.

The Bottom Line

Message authentication codes (MACs) are a common way to insure the integrity of a message and therefore useful for electronic funds transfers (EFTs.) The codes are randomly generated by an algorithm. Financial institutions that a🌌llow transfers of funds typically use MACs as part of their security.

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