Digital Signature vs. MAC

You can use Digital signatures and Message Authentication Code (MAC) to preserve the integrity of a message. However, the benefits of using those two encryption methods are not identical.

In many ways, you get more benefits with digital signatures than with using MAC signatures. Read on to discover the features, similarities, differences, and benefits of using each of the two technologies to encrypt a message.

How a MAC Signature Secures Data

MAC uses symmetric key cryptography, where the sender and receiver of a messenger share the same key. When the sender encrypts the message, they include the generated MAC at the end of the crypto message.

Once the receiver gets the crypto message, they use their key to decrypt the message. They then generate their own MAC from the decrypted message. If their MAC matches the sender’s MAC, then the message is valid.

If the MAC does not match, then the message has been tampered with, and therefore it is invalid. Moreover, the receiver cannot decrypt a MAC encrypted message without the MAC key. Therefore, MAC can be used for authentication.

The length of a MAC text is shorter than that of the plain text it is encrypting. That means it is possible for two messages to end up with the same MAC values. However, the chances of this happening are extremely low.

How a Digital Signature Works

Digital signatures use asymmetric ciphers, where the sender holds a private key while the receiver or receivers get a public key. And since encrypting an entire message can be resource intensive, digital signatures encrypt the message hash instead of the message itself.

The sender then sends both the message and the hash. The recipient can use the public key to decrypt the message hash, verify its integrity, and reveal the sender’s details.

In that regard, a digital signature can securely send a message, authenticate users, determine who sent a message, and check a message’s integrity. That makes a digital signature suitable for securing contracts.

When a public key is used to decrypt a message hash that has been altered, the output is gibberish. And in the case of smart contracts, such a message is discarded. This makes digital signatures valuable for verifying valuable transactions.

Differences between Digital Signature and MAC

Asymmetric Keys and Symmetric Keys

Digital signatures use an asymmetric cryptography, while MAC uses symmetric cryptography. That makes digital signatures more secure when the access keys are shared publicly.

The only way for MAC to rival it is for senders to create new private keys for each new receiver they send a message to.

Easy Secure Communication

With a digital signature, a sender does not have to generate a new private key for each receiver for secure communication. They only need to have their key pairs, the private key for encryption and the public key for decryption.

Identify Message Sender

With MAC, it can be hard to determine the source of the message if two or more people possess that private key. With digital signatures, the private key is not shared. That makes it easy to determine the source or sender of the message.

Secure Boot

This feature is also useful for secure boot because the device can use public, such as the user ID, to verify the boot code’s integrity. It does not need to access the private key that was used to sign the boot code.

Computation Power

The added security of digital signatures means they require more computation power from a device. However, the capability to identify the sender uniquely overshadows that added cost.

MACs can run on light-powered devices. They only require a device that can store a shared private key and support the cryptographic hash function. Their downside is they cannot uniquely identify the sender.

A digital signature can uniquely identify the sender but requires significant computing power. At a minimum, it needs a hardware accelerator to carry out finite field operations.

Overall, for secure communication and integrity verification, digital signatures are a better solution compared to MACs.

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