How do you compare the performance and security of HMAC with other authentication methods?

1 MAC basics

MAC, or message authentication code, is a generic term for any function that produces a signature based on a message and a secret key. The signature can be used to verify that the message has not been tampered with or forged by an attacker. MAC functions can be classified into two types: symmetric and asymmetric. Symmetric MACs use the same key for both generating and verifying signatures, while asymmetric MACs use different keys for each role. HMAC is an example of a symmetric MAC.

2 HMAC advantages

HMAC has several advantages over other symmetric MACs, such as CBC-MAC, CMAC, or GMAC. First, HMAC can use any hash function as its underlying algorithm, which means it can leverage the security and performance of existing hash standards, such as SHA-256 or SHA-3. Second, HMAC is resistant to length extension attacks, which exploit the way some hash functions process messages in blocks. Third, HMAC is easy to implement and has low computational overhead, making it suitable for resource-constrained devices and applications.

3 HMAC limitations

HMAC is not without limitations, however. One of the main drawbacks of HMAC is that it requires both parties to share a secret key in advance, which can be challenging in some scenarios, such as public key infrastructures or distributed systems. Another limitation of HMAC is that it does not provide non-repudiation, which means that the sender cannot prove to a third party that they sent a message with a valid signature. This can be problematic in legal or contractual contexts, where evidence of communication is needed.

4 Digital signatures

Digital signatures are a form of asymmetric MAC that use public key cryptography to generate and verify signatures. The sender uses their private key to sign a message, and the receiver uses the sender's public key to verify it. Digital signatures provide non-repudiation, as the sender cannot deny having signed a message, and the receiver cannot forge a signature without knowing the sender's private key. Digital signatures also do not require a shared secret key, as the public keys can be distributed openly.

5 Digital signature trade-offs

Digital signatures have some trade-offs compared to HMAC, however. One of the main trade-offs is performance, as digital signature algorithms are more complex and computationally intensive than hash functions. This can affect the speed and efficiency of message processing, especially for large or frequent messages. Another trade-off is key management, as digital signatures require a reliable and secure way to generate, store, and distribute public and private keys. This can involve additional protocols, such as certificates, trust models, and revocation mechanisms.

6 Password-based schemes

Password-based schemes are another type of authentication method that use a secret password or passphrase to generate and verify signatures. The password can be derived from a user input, a random string, or a combination of both. Password-based schemes can be implemented using various techniques, such as salted hashes, key derivation functions, or password-authenticated key exchange protocols. Password-based schemes are often used for user authentication, such as logging into a website or a service.

7 Password-based scheme challenges

Password-based schemes have some challenges compared to HMAC, however. One of the main challenges is password security, as passwords can be guessed, cracked, or stolen by attackers. This can compromise the integrity and confidentiality of messages, as well as the identity and privacy of users. Another challenge is password usability, as passwords can be forgotten, lost, or mistyped by users. This can affect the availability and convenience of message exchange, as well as the user experience and satisfaction.

8 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?