SHA vs SHA-3: Understanding the Future of Hashing

From SHA to SHA-3: The Evolution of Hashing Algorithms

 What is Hashing?

At its core, hashing is the process of taking any input (text, image, file, etc.) and converting it into a fixed-length string of characters, usually represented in hexadecimal. This output is called a hash or digest.

For example:

Input: "Hello"
Hash (SHA-256): 185f8db32271fe25f561a6fc938b2e264306ec304eda518007d1764826381969

Notice how:

  • The output length is fixed, no matter the input size.

  • Even a tiny change in input (like “hello” instead of “Hello”) gives a completely different hash.

  • The process is one-way – you cannot reverse a hash back to the original input.

Because of these properties, hashing is widely used in data integrity verification, password storage, blockchain, and digital signatures.

🔹 The Journey from SHA-1 to SHA-2

The Secure Hash Algorithm (SHA) family was developed by NIST (National Institute of Standards and Technology) and NSA.

  1. SHA-1 (1995)

    • Produced a 160-bit hash.

    • Used in SSL certificates, Git, and older systems.

    • Problem: It became vulnerable to collision attacks (where two different inputs produce the same hash). In 2017, Google and CWI Amsterdam demonstrated a practical collision for SHA-1.

  2. SHA-2 (2001)

    • A family including SHA-224, SHA-256, SHA-384, and SHA-512.

    • Stronger and more secure than SHA-1.

    • Still widely used today in TLS/SSL, Bitcoin blockchain (SHA-256), and file integrity checks.

    • Weakness: While still secure, SHA-2 uses the Merkle–Damgård construction, which is considered structurally less resilient against future cryptographic advances.

 Why SHA-3?

By the mid-2000s, cryptographers anticipated that even SHA-2 might eventually be at risk. To future-proof hashing, NIST launched the SHA-3 competition (2007–2012).

The winner was Keccak (pronounced “catch-ack”), designed by Guido Bertoni, Joan Daemen, Michaël Peeters, and Gilles Van Assche.

SHA-3 was standardized in 2015 as FIPS 202.

 How Does SHA-3 Work? (The Algorithm)

Unlike SHA-1 and SHA-2, which use the Merkle–Damgård structure, SHA-3 is built on a sponge construction.

Here’s how it works:

  1. Absorbing Phase

    • The input message is divided into blocks.

    • Each block is XORed into part of the internal state.

    • Then, a permutation function f is applied to the state.

  2. Squeezing Phase

    • Once the input is fully absorbed, the algorithm outputs the hash by “squeezing” bits out of the state.

    • If more bits are needed, f is applied again and more bits are squeezed out.

 Key Features:

  • Configurable output length – unlike SHA-2, SHA-3 can generate variable-length digests.

  • Different internal math – SHA-3 is not just an “upgrade” of SHA-2 but a fundamentally different design.

  • Resistant to length-extension attacks – a known issue in SHA-2.

  • Post-quantum resilience (to some extent) – while not fully quantum-proof, SHA-3 is considered stronger against future cryptanalysis.

🔹 SHA vs SHA-3: A Quick Comparison

Feature SHA-1 SHA-2 (SHA-256) SHA-3 (Keccak)
Year Introduced 1995 2001 2015
Hash Size 160-bit 224, 256, 384, 512-bit Flexible (SHA3-224 to SHA3-512)
Construction Merkle–Damgård Merkle–Damgård Sponge construction
Security Broken (collisions) Secure (widely used) Secure, future-proof
Example Uses Legacy systems Blockchain, TLS, SSL IoT, blockchain extensions, future cryptosystems

🔹 Where is SHA-3 Used Today?

Although SHA-2 is still dominant, SHA-3 adoption is slowly growing in:

  • Blockchain research (Ethereum originally considered it).

  • IoT security where flexible digest size is valuable.

  • Digital signatures & key derivation where resistance to advanced attacks is critical.

🔹 Conclusion

The move from SHA to SHA-3 is not about replacing a broken system (like SHA-1’s case) but about future-proofing security.

  • SHA-2 is still secure today, but SHA-3 provides an alternative design with different mathematical foundations.

  • Think of SHA-3 as a backup plan – if SHA-2 is ever broken, we already have a standardized, battle-tested alternative.

Hashing remains one of the cornerstones of cybersecurity, and the SHA family shows how cryptography evolves to stay ahead of attackers.


Comments

Post a Comment