From 6498b3808c81eeb19f5b1b3a3c8797c1c4adc83a Mon Sep 17 00:00:00 2001 From: Andres Erbsen Date: Thu, 27 Oct 2016 10:12:54 -0400 Subject: put EdDSA encoding sign bit at the MSB --- src/Spec/Ed25519.v | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) (limited to 'src/Spec/Ed25519.v') diff --git a/src/Spec/Ed25519.v b/src/Spec/Ed25519.v index a8e95cf9d..d6873607f 100644 --- a/src/Spec/Ed25519.v +++ b/src/Spec/Ed25519.v @@ -61,12 +61,15 @@ Section Ed25519. (F.of_Z q 15112221349535400772501151409588531511454012693041857206046113283949847762202, F.of_Z q 4 / F.of_Z q 5). - Definition Fencode {b : nat} {m} : F m -> Word.word b := + Local Infix "++" := Word.combine. + Local Notation bit b := (Word.WS b Word.WO : Word.word 1). + + Definition Fencode {len} {m} : F m -> Word.word len := fun x : F m => (Word.NToWord _ (BinIntDef.Z.to_N (F.to_Z x))). Definition sign (x : F q) : bool := BinIntDef.Z.testbit (F.to_Z x) 0. Definition Eenc : E -> Word.word b := fun P => - let '(x,y) := E.coordinates P in Word.WS (sign x) (Fencode y). - Definition Senc : Fl -> Word.word b := Fencode. + let '(x,y) := E.coordinates P in Fencode (len:=b-1) y ++ bit (sign x). + Definition Senc : Fl -> Word.word b := Fencode (len:=b). (* TODO(andreser): prove this after we have fast scalar multplication *) Axiom B_order_l : CompleteEdwardsCurveTheorems.E.eq (BinInt.Z.to_nat l * B)%E E.zero. -- cgit v1.2.3