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Require Import Crypto.Spec.EdDSA Crypto.Spec.Encoding.
Require Import Coq.Numbers.Natural.Peano.NPeano.
Require Import Bedrock.Word.
Require Import Coq.ZArith.Znumtheory Coq.ZArith.BinInt Coq.ZArith.ZArith.
Require Import Crypto.Spec.CompleteEdwardsCurve Crypto.CompleteEdwardsCurve.CompleteEdwardsCurveTheorems.
Require Import Crypto.ModularArithmetic.PrimeFieldTheorems Crypto.ModularArithmetic.ModularArithmeticTheorems.
Require Import Crypto.Util.ListUtil Crypto.Util.CaseUtil Crypto.Util.ZUtil.
Require Import Crypto.Tactics.VerdiTactics.
Local Open Scope nat_scope.
Section EdDSAProofs.
Context {prm:EdDSAParams}.
Existing Instance E.
Existing Instance PointEncoding.
Existing Instance FqEncoding.
Existing Instance FlEncoding.
Existing Instance n_le_b.
Hint Rewrite sign_spec split1_combine split2_combine.
Hint Rewrite Nat.mod_mod using omega.
Ltac arith' := intros; autorewrite with core; try (omega || congruence).
Ltac arith := arith';
repeat match goal with
| [ H : _ |- _ ] => rewrite H; arith'
end.
(* for signature (R_, S_), R_ = encode_point (r * B) *)
Lemma decode_sign_split1 : forall A_ sk {n} (M : word n),
split1 b b (sign A_ sk M) = enc (wordToNat (H (prngKey sk ++ M)) * B)%E.
Proof.
unfold sign; arith.
Qed.
Hint Rewrite decode_sign_split1.
(* for signature (R_, S_), S_ = encode_scalar (r + H(R_, A_, M)s) *)
Lemma decode_sign_split2 : forall sk {n} (M : word n),
split2 b b (sign (public sk) sk M) =
let r : nat := H (prngKey sk ++ M) in (* secret nonce *)
let R : E.point := (r * B)%E in (* commitment to nonce *)
let s : nat := curveKey sk in (* secret scalar *)
let S : F (Z.of_nat l) := ZToField (Z.of_nat (r + H (enc R ++ public sk ++ M) * s)) in
enc S.
Proof.
unfold sign; arith.
Qed.
Hint Rewrite decode_sign_split2.
Hint Rewrite E.add_0_r E.add_0_l E.add_assoc.
Hint Rewrite E.mul_assoc E.mul_add_l E.mul_0_l E.mul_zero_r.
Hint Rewrite plus_O_n plus_Sn_m mult_0_l mult_succ_l.
Hint Rewrite l_order_B.
Lemma l_order_B' : forall x, (l * x * B = E.zero)%E.
Proof.
intros; rewrite Mult.mult_comm. rewrite <- E.mul_assoc. arith.
Qed. Hint Rewrite l_order_B'.
Lemma scalarMult_mod_l : forall n0, (n0 mod l * B = n0 * B)%E.
Proof.
intros.
rewrite (div_mod n0 l) at 2 by (generalize l_odd; omega).
arith.
Qed. Hint Rewrite scalarMult_mod_l.
Hint Rewrite @encoding_valid.
Hint Rewrite @FieldToZ_ZToField.
Hint Rewrite <-mod_Zmod.
Hint Rewrite Nat2Z.id.
Lemma l_nonzero : l <> O. pose l_odd; omega. Qed.
Hint Resolve l_nonzero.
Lemma verify_valid_passes : forall sk {n} (M : word n),
verify (public sk) M (sign (public sk) sk M) = true.
Proof.
unfold verify, sign, public; arith; try break_if; intuition.
Qed.
End EdDSAProofs.
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