GlossaryAdvanced
Preimage Resistance
A property of a secure hash function meaning it's computationally infeasible to work backward from an output to find the original input that produced it.
Preimage resistance is a required property of a cryptographically secure hash function: given only a hash function's output, it must be computationally infeasible to work backward and find an input that produces that exact output.
This property is foundational to how hash functions are used throughout crypto — for example, a Bitcoin address is derived from a public key via hashing, and preimage resistance is exactly what prevents someone from reversing that process to recover the public key from the address alone.
Examples
- Preimage resistance is why knowing a hash output doesn't let an attacker work backward to discover the original data that was hashed.
- A hash function lacking preimage resistance would be unsuitable for the security guarantees crypto applications depend on, including address derivation.