Is there a SHA that s guaranteed to produce a unique hash

Question

I’m trying to understand if there’s a SHA (Secure Hash Algorithm) variant that guarantees unique hashes for different data inputs. I know hash collisions are rare but possible in hashing algorithms, and I want to know which SHA variant might minimize this risk for unique identifiers.

Is there a recommended SHA variant, or should I consider alternatives if I need a guarantee against collisions?

Answer 1

No cryptographic hash function, including SHA, can guarantee a unique hash for every possible input due to the pigeonhole principle. However, some SHA variants have a very low probability of collisions, making them highly reliable for practical purposes.

SHA Variants and Collision Resistance

• SHA-256 and SHA-512 are secure hash functions with very low collision probabilities. 
• SHA-256 produces a 256-bit hash, while SHA-512 produces a 512-bit hash, offering even more security. 
• Both are highly resistant to collisions but can't guarantee uniqueness due to the finite output size. 
• The risk of collisions is practically negligible for most applications.

Can You Get a Guaranteed Unique Hash?

If you absolutely require a guarantee against hash collisions, no standard cryptographic hash function will meet that requirement because of the finite output size. The best approach would be to combine the cryptographic hash function with other techniques.

Alternatives to SHA

If uniqueness is critical, consider alternatives like UUIDs or GUIDs, which are designed to guarantee uniqueness without the risk of collisions, although they do not provide cryptographic security or a hash.

Comments

It could be useful to highlight specific real-world examples where collision resistance suffices, such as file integrity verification or digital signatures, to make the explanation more relatable.