From 102953da274c135124f27b5b68a96271786b0f8b Mon Sep 17 00:00:00 2001
From: dignifiedquire <me@dignifiedquire.com>
Date: Sat, 2 Dec 2023 13:21:15 +0100
Subject: [PATCH] cache boxedresiduie for qinv

---
 src/algorithms/rsa.rs |  1 -
 src/key.rs            | 14 +++++++-------
 src/traits/keys.rs    |  9 ++++++---
 3 files changed, 13 insertions(+), 11 deletions(-)

diff --git a/src/algorithms/rsa.rs b/src/algorithms/rsa.rs
index f626338e..77cf681a 100644
--- a/src/algorithms/rsa.rs
+++ b/src/algorithms/rsa.rs
@@ -95,7 +95,6 @@ pub fn rsa_decrypt<R: CryptoRngCore + ?Sized>(
         let x = m1r.sub(&m2r);
 
         // precomputed: qInv = (1/q) mod p
-        let qinv = BoxedResidue::new(&qinv, p_params.clone());
 
         // h = qInv.(m1 - m2) mod p
         let h = qinv.mul(&x).retrieve();
diff --git a/src/key.rs b/src/key.rs
index d75309a5..3f1ee820 100644
--- a/src/key.rs
+++ b/src/key.rs
@@ -111,7 +111,7 @@ pub(crate) struct PrecomputedValues {
     /// D mod (Q-1)
     pub(crate) dq: BoxedUint,
     /// Q^-1 mod P
-    pub(crate) qinv: BoxedUint,
+    pub(crate) qinv: BoxedResidue,
 
     pub(crate) p_params: BoxedResidueParams,
     pub(crate) q_params: BoxedResidueParams,
@@ -121,7 +121,6 @@ impl Zeroize for PrecomputedValues {
     fn zeroize(&mut self) {
         self.dp.zeroize();
         self.dq.zeroize();
-        self.qinv.zeroize();
     }
 }
 
@@ -436,19 +435,20 @@ impl RsaPrivateKey {
 
         // TODO: error handling
 
+        let p_params = BoxedResidueParams::new(p.clone()).unwrap();
+        let q_params = BoxedResidueParams::new(q.clone()).unwrap();
+
         let x = NonZero::new(p.wrapping_sub(&BoxedUint::one())).unwrap();
         let dp = d.rem_vartime(&x);
         let x = NonZero::new(q.wrapping_sub(&BoxedUint::one())).unwrap();
         let dq = d.rem_vartime(&x);
-        let qinv = q.inv_mod(p);
+        let qinv = BoxedResidue::new(q, p_params.clone());
+        let qinv = qinv.invert();
         if qinv.is_none().into() {
             return Err(Error::InvalidPrime);
         }
         let qinv = qinv.unwrap();
 
-        let p_params = BoxedResidueParams::new(p.clone()).unwrap();
-        let q_params = BoxedResidueParams::new(q.clone()).unwrap();
-
         self.precomputed = Some(PrecomputedValues {
             dp,
             dq,
@@ -570,7 +570,7 @@ impl PrivateKeyPartsNew for RsaPrivateKey {
         self.precomputed.as_ref().map(|p| &p.dq)
     }
 
-    fn qinv(&self) -> Option<&BoxedUint> {
+    fn qinv(&self) -> Option<&BoxedResidue> {
         self.precomputed.as_ref().map(|p| &p.qinv)
     }
 
diff --git a/src/traits/keys.rs b/src/traits/keys.rs
index 7d4afbce..671d0647 100644
--- a/src/traits/keys.rs
+++ b/src/traits/keys.rs
@@ -2,7 +2,10 @@
 
 use alloc::vec::Vec;
 
-use crypto_bigint::{modular::BoxedResidueParams, BoxedUint, NonZero};
+use crypto_bigint::{
+    modular::{BoxedResidue, BoxedResidueParams},
+    BoxedUint, NonZero,
+};
 use num_bigint::{BigInt, BigUint, IntoBigInt};
 use num_traits::FromPrimitive;
 use zeroize::Zeroize;
@@ -98,7 +101,7 @@ impl<T: PrivateKeyPartsNew> PrivateKeyParts for T {
         PrivateKeyPartsNew::dq(self).map(to_biguint)
     }
     fn qinv(&self) -> Option<BigInt> {
-        PrivateKeyPartsNew::qinv(self).and_then(|v| to_biguint(v).into_bigint())
+        PrivateKeyPartsNew::qinv(self).and_then(|v| to_biguint(&v.retrieve()).into_bigint())
     }
 
     fn crt_values(&self) -> Option<Vec<CrtValue>> {
@@ -121,7 +124,7 @@ pub trait PrivateKeyPartsNew: PublicKeyPartsNew {
     fn dq(&self) -> Option<&BoxedUint>;
 
     /// Returns the precomputed qinv value, Q^-1 mod P
-    fn qinv(&self) -> Option<&BoxedUint>;
+    fn qinv(&self) -> Option<&BoxedResidue>;
 
     /// Returns an iterator over the CRT Values
     fn crt_values(&self) -> Option<&[CrtValueNew]>;