FAC ⊆ TFNP

FAC is contained in TFNP.

Statement

Migrated verbatim from total-function-np § Relevance to cryptography:

Integer factorization and discrete logarithm — the two most historically important hard problems in cryptography — are both in TFNP, formalizing the intuition that they are “hard search problems with guaranteed solutions.” Recent work has used TFNP subclass hardness (especially PPAD) as a basis for constructing cryptographic primitives from weaker or more structured assumptions.

Notes

source: folklore: the claim carried no citation on the page it was migrated from, and none was invented.

class: unstated: no citing page says which notion of reduction is meant. Recording a class the wiki does not state would add a claim.

class: free because a containment between complexity classes is proved by any argument at all; the reduction-class axis does not discriminate here, and unstated would wrongly suggest the information is missing.

Recorded during migration and not fixed — these are claims about the source text, not changes to it:

  • Uncited.
  • [[factoring]] is not wikilinked although content/Assumptions/factoring.md exists.
  • ‘the two most historically important hard problems in cryptography’ is marketing prose (house-style anti-pattern).