What distinguishes HMAC-SHA256 from SHA-256 in terms of functionality and security? (2024)

HMAC-SHA256 and SHA-256 are both cryptographic algorithms used for hashing data. However, they have distinct differences in terms of functionality and security.

Functionality:

1. SHA-256 (Secure Hash Algorithm 256-bit) is a standalone hash function that takes an input and produces a fixed-size output of 256 bits. It is commonly used for data integrity checks and digital signatures.
2. HMAC-SHA256 (Hash-based Message Authentication Code with SHA-256) is a specific construction that combines the SHA-256 hash function with a secret key. It provides a way to verify the integrity and authenticity of a message using a shared key.

Security:

1. SHA-256:

   • SHA-256 is vulnerable to length extension attacks [2]. This means that given the hash of a message, an attacker can easily compute the hash of an extended message without knowing the original message or the secret key.
   • SHA-256 is also susceptible to collision attacks, where two different inputs produce the same hash output [3]. However, finding such collisions is computationally expensive and currently not feasible.
   • SHA-256 is considered secure for most practical purposes and is widely used in various applications.

2. HMAC-SHA256:

   • HMAC-SHA256 is designed to overcome the vulnerabilities of SHA-256 by incorporating a secret key into the hashing process.
   • The secret key used in HMAC-SHA256 adds an additional layer of security, making it resistant to length extension attacks [2].
   • HMAC-SHA256 is also resistant to collision attacks, as long as the underlying hash function (SHA-256) remains secure.
   • The use of a secret key in HMAC-SHA256 provides message authentication, ensuring that the message has not been tampered with and that it originated from a trusted source.

In summary, HMAC-SHA256 provides stronger security guarantees compared to SHA-256 alone. By incorporating a secret key, HMAC-SHA256 protects against length extension attacks and provides message authentication. However, both algorithms are widely used and considered secure for most practical purposes.

Learn more:

1. What's the difference between HMAC-SHA256(key, data) and SHA256(key + data) - Information Security Stack Exchange
2. How is HMAC SHA-256 different from SHA256? - Learn & Grow with Popular eLearning Community - JanBask
3. HMAC SHA256 vs RSA SHA256 - which one to use - Cryptography Stack Exchange