No free reduction from GGM to DLOG
A reduction of class free from GGM to DLOG would imply a contradiction.
Statement
Migrated verbatim from generic-group-model § Shoup’s Formulation:
The key result of Sho97 is that any generic algorithm solving DLOG, CDH, or DDH in a group of prime order must issue oracle queries. Combined with the Baby-step Giant-step algorithm, this is tight.
Migrated verbatim from discrete-logarithm § Known Results:
- In the Generic Group Model, , where is the number of queries that issues — Sho97
Notes
Recorded during migration and not fixed — these are claims about the source text, not changes to it:
- THREE CONCLUSIONS IN ONE SENTENCE (DLOG, CDH, DDH). Recorded as three separate edges on line 23 — these are three independent lower bounds, not one conjunctive claim.
- A query lower bound in an idealized model is not a reduction: it is unconditional hardness relative to the model, so ‘hypotheses’ is really ‘the adversary is generic’, not another assumption.
- The Sho97 DDH lower bound holds in prime-order groups without pairings; the sentence’s ‘in a group of prime order ’ does not exclude pairing-friendly groups, where DDH is easy — the genericity restriction is what saves it, but a reader could take the bound too broadly.
- Three near-identical copies of the same Sho97 theorem across dlog / ddh / cdh pages, differing only in the superscript on Adv. A fourth statement of the same bound sits at content/Glossary/generic-group-model.md:23 in the Omega(sqrt(p))-queries form rather than the O(q^2/p)-advantage form.
- This is a MODEL-RELATIVE LOWER BOUND, not a reduction barrier. It is a hardness result inside an idealized model, which the barrier schema shoehorns into consequenceKind ‘contradiction’. A separate ‘idealized-model lower bound’ record type would fit better.
- The DDH copy is the shakiest: the O(q^2/p) generic bound for DDH requires more care than for DLOG/CDH and the page states it identically to the other two without comment.
- Fourth copy of the Sho97 bound, stated in the Omega(sqrt(p))-query form. The three Assumptions-page copies use the O(q^2/p)-advantage form. Neither form links to the other.
- Bundles DLOG, CDH, and DDH into one sentence — three separate conclusions under one hypothesis, which the hyperedge model requires be split into three barriers.