From 98a86a238949ae5e97b3155b0418b1e84e5223fc Mon Sep 17 00:00:00 2001
From: dignifiedquire <me@dignifiedquire.com>
Date: Wed, 29 Nov 2023 16:36:26 +0100
Subject: [PATCH] implement blinding (tests failing currently)

---
 src/algorithms/rsa.rs | 19 +++++++++----------
 src/key.rs            |  4 ++--
 src/pkcs1v15.rs       |  4 +---
 3 files changed, 12 insertions(+), 15 deletions(-)

diff --git a/src/algorithms/rsa.rs b/src/algorithms/rsa.rs
index 2c93b576..3d748abe 100644
--- a/src/algorithms/rsa.rs
+++ b/src/algorithms/rsa.rs
@@ -3,7 +3,7 @@
 use alloc::borrow::Cow;
 use alloc::vec::Vec;
 use crypto_bigint::modular::BoxedResidueParams;
-use crypto_bigint::{BoxedUint, NonZero, Zero};
+use crypto_bigint::{BoxedUint, NonZero};
 use num_bigint::{BigInt, BigUint, IntoBigInt, IntoBigUint, ModInverse, RandBigInt, ToBigInt};
 use num_integer::{sqrt, Integer};
 use num_traits::{FromPrimitive, One, Pow, Signed, Zero as _};
@@ -326,22 +326,23 @@ pub(crate) fn compute_private_exponent_carmicheal(
     }
 }
 
-fn blind_new<R: CryptoRngCore, K: PublicKeyParts>(
+fn blind_new<R: CryptoRngCore, K: PublicKeyPartsNew>(
     rng: &mut R,
     key: &K,
     c: &BoxedUint,
     n_params: &BoxedResidueParams,
 ) -> (BoxedUint, BoxedUint) {
-    let n = NonZero::new(to_uint(key.n().clone())).unwrap();
     let mut r: BoxedUint;
     let mut ir: CtOption<BoxedUint>;
     let unblinder;
     loop {
-        r = todo!(); // BoxedUint::random_mod(&mut rng, &n);
+        // TODO: use constant time gen
+        r = to_uint(rng.gen_biguint_below(&to_biguint(&key.n())));
+        // TODO: correct mapping
         if r.is_zero().into() {
             r = BoxedUint::one();
         }
-        ir = r.inv_mod(&n);
+        ir = r.inv_mod(key.n());
 
         // TODO: constant time?
         if let Some(ir) = ir.into() {
@@ -350,13 +351,12 @@ fn blind_new<R: CryptoRngCore, K: PublicKeyParts>(
         }
     }
 
-    let e = to_uint(key.e().clone());
     let c = {
         let r = reduce(&r, n_params.clone());
-        let rpowe = r.pow(&e).retrieve();
+        let mut rpowe = r.pow(key.e()).retrieve();
 
         let c = c.wrapping_mul(&rpowe);
-        let c = c.rem_vartime(&n);
+        let c = c.rem_vartime(key.n());
 
         rpowe.zeroize();
 
@@ -367,9 +367,8 @@ fn blind_new<R: CryptoRngCore, K: PublicKeyParts>(
 }
 
 fn unblind_new(key: &impl PublicKeyPartsNew, m: &BoxedUint, unblinder: &BoxedUint) -> BoxedUint {
-    let n = key.n();
     let a = m.wrapping_mul(unblinder);
-    a.rem_vartime(&n)
+    a.rem_vartime(key.n())
 }
 
 pub fn rsa_decrypt_new<R: CryptoRngCore + ?Sized>(
diff --git a/src/key.rs b/src/key.rs
index 302952f0..fb15e84d 100644
--- a/src/key.rs
+++ b/src/key.rs
@@ -4,7 +4,7 @@ use core::hash::{Hash, Hasher};
 use crypto_bigint::modular::{BoxedResidue, BoxedResidueParams};
 use crypto_bigint::{BoxedUint, Limb, NonZero};
 use num_bigint::traits::ModInverse;
-use num_bigint::{BigInt, BigUint};
+use num_bigint::BigUint;
 use num_integer::Integer;
 use num_traits::{FromPrimitive, One, ToPrimitive};
 use rand_core::CryptoRngCore;
@@ -272,7 +272,7 @@ impl RsaPrivateKey {
         n: BigUint,
         e: BigUint,
         d: BigUint,
-        mut primes: Vec<BigUint>,
+        primes: Vec<BigUint>,
     ) -> Result<RsaPrivateKey> {
         let mut should_validate = false;
         let mut primes: Vec<_> = primes.into_iter().map(to_uint).collect();
diff --git a/src/pkcs1v15.rs b/src/pkcs1v15.rs
index d3a47be4..7f4d2f3c 100644
--- a/src/pkcs1v15.rs
+++ b/src/pkcs1v15.rs
@@ -389,9 +389,7 @@ mod tests {
             assert_ne!(input, ciphertext);
 
             let blind: bool = rng.next_u32() < (1u32 << 31);
-            // TODO:
-            // let blinder = if blind { Some(&mut rng) } else { None };
-            let blinder: Option<&mut ChaCha8Rng> = None;
+            let blinder = if blind { Some(&mut rng) } else { None };
             let plaintext = decrypt_new(blinder, &priv_key, &ciphertext).unwrap();
             assert_eq!(input, plaintext);
         }