induction ls; intros; simpl in *;
subst; try discriminate.
destruct a.
case_eq (findCollision_1 eqd1 eqd2 ls a b0); intros.
rewrite H0 in H.
eapply findCollision_1_correct in H0.
intuition.
subst.
inversion H; clear H; subst.
intuition.
inversion H; clear H; subst.
intuition.
inversion H; clear H; subst.
intuition.
rewrite H0 in H.
eapply IHls in H.
intuition.
Qed.

Theorem G2_3_bad_equiv :
Pr[x <-$ G2_3; ret (snd x)] == Pr[G2_3_bad].