Merge pull request zkcrypto#2 from xavierdmello/main

feat: patch decompress_pubkey & add from_hex

Cargo.toml

@@ -15,6 +15,9 @@ edition = "2021"
 [package.metadata.docs.rs]
 rustdoc-args = [ "--html-in-header", "katex-header.html" ]
 
+[dependencies]
+sp1_precompiles = { git = "https://github.com/succinctlabs/sp1.git", package = "sp1-precompiles" }
+
 [dev-dependencies]
 csv = ">= 1.0, < 1.2" # csv 1.2 has MSRV 1.60
 criterion = "0.3"

rust-toolchain.toml

@@ -1,3 +1,3 @@
 [toolchain]
-channel = "1.56.0"
-components = [ "clippy", "rustfmt" ]
+channel = "nightly-2024-04-17"
+components = ["llvm-tools", "rustc-dev"]

src/g1.rs

@@ -10,7 +10,7 @@ use group::{
 };
 use rand_core::RngCore;
 use subtle::{Choice, ConditionallySelectable, ConstantTimeEq, CtOption};
-
+use sp1_precompiles::bls12381::decompress_pubkey;
 #[cfg(feature = "alloc")]
 use group::WnafGroup;
 
@@ -330,9 +330,11 @@ impl G1Affine {
     /// for details about how group elements are serialized.
     pub fn from_compressed(bytes: &[u8; 48]) -> CtOption<Self> {
         // We already know the point is on the curve because this is established
-        // by the y-coordinate recovery procedure in from_compressed_unchecked().
+        // by the y-coordinate recovery procedure in decompress_pubkey().
+        let decompressed = decompress_pubkey(bytes).unwrap();
 
-        Self::from_compressed_unchecked(bytes).and_then(|p| CtOption::new(p, p.is_torsion_free()))
+        // Extra checks do not have to be done because because the precompile already does it for us.
+        G1Affine::from_uncompressed_unchecked(&decompressed)
     }
 
     /// Attempts to deserialize an uncompressed element, not checking if the

src/scalar.rs

@@ -335,6 +335,28 @@ impl Scalar {
     pub const fn from_raw(val: [u64; 4]) -> Self {
         (&Scalar(val)).mul(&R2)
     }
+
+    /// Converts from a hex string into its `Scalar` representation.
+    pub fn from_hex(hex: &str) -> Option<Self> {
+        if hex.len() != 64 {
+            return None;
+        }
+
+        let mut raw = [0u64; 4];
+        for (i, chunk) in hex.as_bytes().chunks(16).enumerate().take(4) {
+            if let Ok(hex_chunk) = core::str::from_utf8(chunk) {
+                if let Ok(value) = u64::from_str_radix(hex_chunk, 16) {
+                    raw[3 - i] = value.to_le();
+                } else {
+                    return None;
+                }
+            } else {
+                return None;
+            }
+        }
+
+        Some(Scalar::from_raw(raw))
+    }
 
     /// Squares this element.
     #[inline]