[BROKEN] Start adding support for ECDSA public keys.

src/ecdsa/public.rs

@@ -0,0 +1,68 @@
+use cryptonum::signed::*;
+use cryptonum::unsigned::*;
+use digest::{BlockInput,Digest,Input,FixedOutput,Reset};
+use dsa::rfc6979::{DSASignature,KIterator,bits2int};
+use ecdsa::curve::{EllipticCurve,P192,P224,P256,P384,P521};
+use ecdsa::point::{ECCPoint,Point};
+use hmac::{Hmac,Mac};
+use std::cmp::min;
+
+pub struct ECCPublic<Curve: EllipticCurve> {
+    q: Point<Curve>
+}
+
+pub trait ECCPublicKey {
+    type Curve : EllipticCurve;
+    type Unsigned;
+
+    fn new(d: Point<Self::Curve>) -> Self;
+    fn verify<Hash>(&self, m: &[u8], sig: DSASignature<Self::Unsigned>) -> bool
+      where
+       Hash: BlockInput + Clone + Default + Digest + FixedOutput + Input + Reset,
+       Hmac<Hash>: Mac;
+}
+
+impl ECCPublicKey for ECCPublic<P192>
+{
+    type Curve = P192;
+    type Unsigned = U192;
+
+    fn new(q: Point<P192>) -> ECCPublic<P192>
+    {
+        ECCPublic{ q }
+    }
+
+    fn verify<Hash>(&self, m: &[u8], sig: DSASignature<Self::Unsigned>) -> bool
+      where
+       Hash: BlockInput + Clone + Default + Digest + FixedOutput + Input + Reset,
+       Hmac<Hash>: Mac
+    {
+        let n = <P192>::n();
+
+        if sig.r.is_zero() || (sig.r >= n) {
+            return false;
+        }
+
+        if sig.s.is_zero() || (sig.s >= n) {
+            return false;
+        }
+
+        // e = the leftmost min(N, outlen) bits of Hash(M').
+        let mut digest_bytes = <Hash>::digest(m).to_vec();
+        let len = min(digest_bytes.len(), P192::size() / 8);
+        digest_bytes.truncate(len);
+
+        if let Some(c) = sig.s.modinv(&n) {
+            let e = U192::from_bytes(&digest_bytes);
+            let u1 = e.modmul(&c, &n);
+            let u2 = sig.r.modmul(&c, &n);
+            let g = Point::<P192>::default();
+            let u1i = I192::from(u1);
+            let u2i = I192::from(u2);
+            let point = Point::<P192>::double_scalar_mult(&u1i, &g, &u2i, &self.q);
+            !point.x.is_negative() && (sig.r == U192::from(point.x))
+        } else {
+            false
+        }
+    }
+}