fix: hint if the point can be decompressed

Cargo.toml

@@ -10,3 +10,8 @@ resolver = "2"
 [profile.dev]
 opt-level = 2
 
+
+[patch.crates-io]
+sp1-lib = { git = "https://github.com/succinctlabs/sp1", branch = "n/fix-eddcompress" }
+sp1-curves = { git = "https://github.com/succinctlabs/sp1", branch = "n/fix-eddcompress" }
+

curve25519-dalek/Cargo.toml

@@ -63,6 +63,7 @@ fiat-crypto = { version = "0.2.1", default-features = false }
 
 [target.'cfg(all(target_os = "zkvm", target_vendor = "succinct"))'.dependencies]
 sp1-lib = "3.0.0"
+sp1-curves = "3.0.0"
 anyhow = "1.0"
 
 [features]

curve25519-dalek/src/edwards.rs

@@ -230,12 +230,22 @@ impl CompressedEdwardsY {
         self.0
     }
 
-    #[cfg(not(all(target_os = "zkvm", target_vendor = "succinct")))]
     /// Attempt to decompress to an `EdwardsPoint`.
     ///
     /// Returns `None` if the input is not the \\(y\\)-coordinate of a
     /// curve point.
     pub fn decompress(&self) -> Option<EdwardsPoint> {
+        #[cfg(all(target_os = "zkvm", target_vendor = "succinct"))]
+        {
+            sp1_lib::unconstrained! {
+                sp1_lib::io::write(sp1_lib::io::FD_EDDECOMPRESS, self.as_bytes()); 
+            }
+
+            if sp1_lib::io::read_vec().first().expect("We should have a status from the hook") == &1 {
+                return Some(self.decompress_with_syscall());
+            }
+        }
+
         let (is_valid_y_coord, X, Y, Z) = decompress::step_1(self);
 
         if is_valid_y_coord.into() {
@@ -252,7 +262,7 @@ impl CompressedEdwardsY {
     /// curve point.
     /// 
     /// Accelerated with SP1's EdDecompress syscall.
-    pub fn decompress(&self) -> Option<EdwardsPoint> {
+    fn decompress_with_syscall(&self) -> EdwardsPoint {
         let mut XY_bytes = [0_u8; 64];
         XY_bytes[32..].copy_from_slice(self.as_bytes());
         unsafe {
@@ -261,12 +271,13 @@ impl CompressedEdwardsY {
         let X = FieldElement::from_bytes(&XY_bytes[0..32].try_into().unwrap());
         let Y = FieldElement::from_bytes(&XY_bytes[32..].try_into().unwrap());
         let Z = FieldElement::ONE;
-        return Some(EdwardsPoint {
+
+        EdwardsPoint {
             X,
             Y,
             Z,
             T: &X * &Y,
-        });
+        }
     }
 }
 

curve25519-dalek/src/lib.rs

@@ -59,9 +59,6 @@ extern crate alloc;
 #[macro_use]
 extern crate std;
 
-#[cfg(all(target_os = "zkvm", target_vendor = "succinct"))]
-extern crate sp1_lib;
-
 #[cfg(feature = "digest")]
 pub use digest;