From 79ab6c29bd90c37d89a34a6279b92ae594c44e94 Mon Sep 17 00:00:00 2001
From: Elichai Turkel <elichai.turkel@gmail.com>
Date: Tue, 30 Jul 2024 08:51:44 +0300
Subject: [PATCH] curve: Implement ConditionallySelectable for MontgomeryPoint
 (#677)

---
 curve25519-dalek/Cargo.toml        | 2 +-
 curve25519-dalek/src/montgomery.rs | 6 ++++++
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/curve25519-dalek/Cargo.toml b/curve25519-dalek/Cargo.toml
index f0896ba74..c4fb28a38 100644
--- a/curve25519-dalek/Cargo.toml
+++ b/curve25519-dalek/Cargo.toml
@@ -51,7 +51,7 @@ ff = { version = "0.13", default-features = false, optional = true }
 group = { version = "0.13", default-features = false, optional = true }
 rand_core = { version = "0.6.4", default-features = false, optional = true }
 digest = { version = "0.10", default-features = false, optional = true }
-subtle = { version = "2.6.0", default-features = false }
+subtle = { version = "2.6.0", default-features = false, features = ["const-generics"]}
 serde = { version = "1.0", default-features = false, optional = true, features = ["derive"] }
 zeroize = { version = "1", default-features = false, optional = true }
 
diff --git a/curve25519-dalek/src/montgomery.rs b/curve25519-dalek/src/montgomery.rs
index 2be35cdc7..cb5e2fb87 100644
--- a/curve25519-dalek/src/montgomery.rs
+++ b/curve25519-dalek/src/montgomery.rs
@@ -84,6 +84,12 @@ impl ConstantTimeEq for MontgomeryPoint {
     }
 }
 
+impl ConditionallySelectable for MontgomeryPoint {
+    fn conditional_select(a: &Self, b: &Self, choice: Choice) -> Self {
+        Self(<[u8; 32]>::conditional_select(&a.0, &b.0, choice))
+    }
+}
+
 impl PartialEq for MontgomeryPoint {
     fn eq(&self, other: &MontgomeryPoint) -> bool {
         self.ct_eq(other).into()