hash redc with dkim, compose two u120 limbs into one felt to offset d…

…oubled hash cost

lib/src/lib.nr

@@ -43,18 +43,26 @@ global EMAIL_ADDRESS_CHAR_TABLE: [u8; 123] = [
  * Standard outputs that essentially every email circuit will need to export (alongside app-specific outputs)
  * @notice if you only need the pubkey hash just import pedersen and hash away 
  *
- * @param pubkey - the BN limbs of the DKIM RSA pubkey
+ * @param pubkey - the pubkey redc and modulus limbs
  * @param signature - the BN limbs of the DKIM RSA signature
  * @returns
  *        0: Pedersen hash of DKIM public key (root of trust)
  *        1: Pedersen hash of DKIM signature (email nullifier)
  */
-pub fn standard_outputs<let KEY_BYTE_LENGTH: u32>(
-    pubkey: [Field; KEY_BYTE_LENGTH],
-    signature: [Field; KEY_BYTE_LENGTH],
+pub fn standard_outputs<let KEY_LIMBS: u32>(
+    pubkey: RSAPubkey<KEY_LIMBS>,
+    signature: [Field; KEY_LIMBS],
 ) -> [Field; 2] {
     // create pedersen hash of DKIM signing key to minimize public outputs
-    let pubkey_hash = pedersen_hash(pubkey);
+    let mut dkim_preimage: [Field; 18] = [0; 18];
+
+    for i in 0..9 {
+        let modulus_hi = pubkey.modulus[i * 2] * 2.pow_32(120);
+        let redc_hi = pubkey.redc[i * 2] * 2.pow_32(120);
+        dkim_preimage[i] = modulus_hi + pubkey.modulus[i * 2 + 1];
+        dkim_preimage[i + 9] = redc_hi + pubkey.redc[i * 2 + 1];
+    }
+    let pubkey_hash = pedersen_hash(dkim_preimage);
     // create email nullifier for email
     let email_nullifier = pedersen_hash(signature);
     // output the root of trust and email nullifier