RSA signature verification.

src/rsa/public.rs

@@ -1,5 +1,6 @@
 use cryptonum::{BarrettUCN,UCN};
-use rsa::core::ACCEPTABLE_KEY_SIZES;
+use rsa::core::{ACCEPTABLE_KEY_SIZES,pkcs1_pad,vp1};
+use rsa::signing_hashes::SigningHash;
 
 #[derive(Clone,Debug,PartialEq,Eq)]
 pub struct RSAPublic {
@@ -16,7 +17,7 @@ impl RSAPublic {
         let len = n.bits();
 
         for &(valid_bits, _) in ACCEPTABLE_KEY_SIZES.iter() {
-            if valid_bits > len {
+            if valid_bits >= len {
                 return RSAPublic{
                     byte_len: valid_bits / 8,
                     n: n.clone(),
@@ -27,4 +28,15 @@ impl RSAPublic {
         }
         panic!("Invalid RSA key size in new()")
     }
+
+    /// Verify the signature for a given message, using the given signing hash,
+    /// returning true iff the signature validates.
+    pub fn verify(&self, shash: &SigningHash, msg: &[u8], sig: &[u8]) -> bool {
+        let hash = (shash.run)(msg);
+        let s    = UCN::from_bytes(&sig);
+        let m    = vp1(&self.nu, &self.e, &s);
+        let em   = m.to_bytes(self.byte_len);
+        let em_  = pkcs1_pad(&shash.ident, &hash, self.byte_len);
+        (em == em_)
+    }
 }