Hash Collision
Updated 2026-08-06
INTRODUCTION
English translation pending.
CORE DEFINITION
A hash collision occurs when a hash function maps two distinct inputs to the same output. Collisions are unavoidable in principle by the pigeonhole principle, since the output space is smaller than the input space. What matters in practice is whether collisions can be found efficiently: a secure cryptographic hash makes deliberate collisions computationally infeasible, while MD5 and SHA-1 have both been broken by practical collision attacks. Collision resistance is therefore the property being engineered.
SCAFFOLDING EFFECT
Reduce cognitive load
- Check resolution: ask how many distinct inputs your evaluation collapses into one verdict. - Test for forgery: determine whether someone can construct an input that passes as another. - Add dimensions: distinguish cases the metric currently merges into a single score.
Anchor fast decisions
Any scoring or hashing scheme maps a large space of inputs into a smaller space of outputs, so distinct cases necessarily share a result. When that mapping is public and cheap to compute, an adversary can search for an input that produces a chosen output and pass it off as the original. Collision resistance raises the cost of that search beyond what an attacker can afford.
MINIMUM ACTION
In progress 0/1Practice this model in one real situation:
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Source support: Explicit
- en.wikipedia.orghttps://en.wikipedia.org/wiki/Hash_collisionverified
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