Pre-image resistance
Pre-image resistance is the property that it is computationally infeasible to find an input producing a specified hash output.
Real-World Cryptography
Pre-image resistance is the property that, given a hash output, it is computationally infeasible to find an input that hashes to that output.
- How it is used
- Explains when a published digest can conceal its input and when predictable inputs make guessing practical.
- How deep it goes
- Defines one-wayness, demonstrates exhaustive guessing, and distinguishes second pre-image and collision resistance without proving internals.
- Examples
- Uses a blender analogy, yes/no choices, predictable sentences, and tiny two-bit digests to expose weaknesses.
- What you can do after
- Evaluate whether a hashing use meaningfully hides an input or merely disguises a small, predictable candidate set.
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Hacking Cryptography
The security property that makes it computationally infeasible to find an input corresponding to a specified hash output.
- How it is used
- Defines the one-way security goal used to protect password hashes and support trustworthy digest-based verification.
- How deep it goes
- Defines the attacker’s target and distinguishes it from related properties, but does not develop a concrete inversion algorithm.
- Examples
- Uses password digests, reverse-looked-up password dictionaries, and fixed-size hash outputs as concrete illustrations.
- What you can do after
- Evaluate hash security claims by distinguishing reversal of a chosen digest from second-preimage and collision attacks.
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Related concepts
- hash-based signature schemeused by · A hash-based signature scheme is a digital signature scheme whose security is based on cryptographic hash-function properties rather than algebraic number-theoretic assumptions.
- hash functionproduced by · A hash function deterministically maps input data to a value in a bounded output range, commonly for indexing, lookup, comparison, or integrity checking.
- security propertykind of · A security property is a security-relevant characteristic that a cryptographic primitive or protocol is intended to provide.
- second pre-image resistancecontrasts with · Second pre-image resistance is the property that, given an input and its hash, finding a different input with the same hash is computationally infeasible.
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