Display point in base58 (#305)

* Compress EC subgroup points before serialising

* serialize and display point in base58

* Use Display for Points

---------

Co-authored-by: Ahmad <root@ahmadafuni.com>

Cargo.toml

@@ -23,6 +23,7 @@ plonky2 = { git = "https://github.com/0xPolygonZero/plonky2", optional = true }
 serde = "1.0.219"
 serde_json = "1.0.140"
 base64 = "0.22.1"
+bs58 = "0.5.1"
 schemars = "0.8.22"
 num = { version = "0.4.3", features = ["num-bigint"] }
 num-bigint = { version = "0.4.6", features = ["rand"] }

examples/signed_pod.rs

@@ -15,7 +15,7 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
     // Create a schnorr key pair to sign the pod
     let sk = SecretKey::new_rand();
     let pk = sk.public_key();
-    println!("Public key: {:?}\n", pk);
+    println!("Public key: {}\n", pk);
 
     let mut signer = Signer(sk);
 

src/backends/plonky2/primitives/ec/curve.rs

@@ -3,7 +3,7 @@
 //! We roughly follow pornin/ecgfp5.
 use core::ops::{Add, Mul};
 use std::{
-    array,
+    array, fmt,
     ops::{AddAssign, Neg, Sub},
     sync::LazyLock,
 };
@@ -23,7 +23,7 @@ use plonky2::{
     util::serialization::{Read, Write},
 };
 use rand::rngs::OsRng;
-use serde::{Deserialize, Serialize};
+use serde::{Deserialize, Deserializer, Serialize, Serializer};
 
 use crate::backends::plonky2::{
     circuits::common::ValueTarget,
@@ -94,12 +94,65 @@ fn ec_field_from_bytes(b: &[u8]) -> Result<ECField, Error> {
     Ok(QuinticExtension(array::from_fn(|i| fields[i])))
 }
 
-#[derive(Clone, Copy, Debug, PartialEq, Eq, Serialize, Deserialize)]
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
 pub struct Point {
     pub x: ECField,
     pub u: ECField,
 }
 
+impl fmt::Display for Point {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        #[allow(clippy::collapsible_else_if)]
+        if f.alternate() {
+            write!(f, "({}, {})", self.x, self.u)
+        } else {
+            if self.is_in_subgroup() {
+                // Compressed
+                let u_bytes = self.as_bytes_from_subgroup().expect("point in subgroup");
+                let u_b58 = bs58::encode(u_bytes).into_string();
+                write!(f, "{}", u_b58)
+            } else {
+                // Non-compressed
+                let xu_bytes = [ec_field_to_bytes(&self.x), ec_field_to_bytes(&self.u)].concat();
+                let xu_b58 = bs58::encode(xu_bytes).into_string();
+                write!(f, "{}", xu_b58)
+            }
+        }
+    }
+}
+
+impl Serialize for Point {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        let point_b58 = format!("{}", self);
+        serializer.serialize_str(&point_b58)
+    }
+}
+
+impl<'de> Deserialize<'de> for Point {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        let point_b58 = String::deserialize(deserializer)?;
+        let point_bytes: Vec<u8> = bs58::decode(point_b58)
+            .into_vec()
+            .map_err(serde::de::Error::custom)?;
+        if point_bytes.len() == 80 {
+            // Non-compressed
+            Ok(Point {
+                x: ec_field_from_bytes(&point_bytes[..40]).map_err(serde::de::Error::custom)?,
+                u: ec_field_from_bytes(&point_bytes[40..]).map_err(serde::de::Error::custom)?,
+            })
+        } else {
+            // Compressed
+            Self::from_bytes_into_subgroup(&point_bytes).map_err(serde::de::Error::custom)
+        }
+    }
+}
+
 impl Point {
     pub fn new_rand_from_subgroup() -> Self {
         &OsRng.gen_biguint_below(&GROUP_ORDER) * Self::generator()
@@ -111,8 +164,8 @@ impl Point {
         match self.is_in_subgroup() {
             true => Ok(self.u),
             false => Err(Error::custom(format!(
-                "Point must lie in EC subgroup: ({}, {})",
+                "Point must lie in EC subgroup: {}",
-                self.x, self.u
+                self
             ))),
         }
     }
@@ -810,7 +863,7 @@ mod test {
             match p == q {
                 true => Ok(()),
                 false => Err(Error::custom(format!(
-                    "Roundtrip compression failed: {:?} ≠ {:?}",
+                    "Roundtrip compression failed: {} ≠ {}",
                     p, q
                 ))),
             }
@@ -897,4 +950,28 @@ mod test {
         assert!(data.prove(pw).is_err());
         Ok(())
     }
+
+    #[test]
+    fn test_point_serialize_deserialize() -> Result<(), anyhow::Error> {
+        // In subgroup
+        let g = Point::generator();
+
+        let serialized = serde_json::to_string_pretty(&g)?;
+        println!("g = {}", serialized);
+        let deserialized = serde_json::from_str(&serialized)?;
+        assert_eq!(g, deserialized);
+
+        // Not in subgroup
+        let not_sub = Point {
+            x: Point::b() / g.x,
+            u: g.u,
+        };
+
+        let serialized = serde_json::to_string_pretty(&not_sub)?;
+        println!("not_sub = {}", serialized);
+        let deserialized = serde_json::from_str(&serialized)?;
+        assert_eq!(not_sub, deserialized);
+
+        Ok(())
+    }
 }

src/middleware/mod.rs

@@ -180,7 +180,7 @@ impl fmt::Display for TypedValue {
             TypedValue::Set(s) => write!(f, "set:{}", s.commitment()),
             TypedValue::Array(a) => write!(f, "arr:{}", a.commitment()),
             TypedValue::Raw(v) => write!(f, "{}", v),
-            TypedValue::PublicKey(p) => write!(f, "ecGFp5_pt:({},{})", p.x, p.u),
+            TypedValue::PublicKey(p) => write!(f, "pk:{}", p),
             TypedValue::PodId(id) => write!(f, "pod_id:{}", id),
         }
     }
@@ -849,6 +849,7 @@ pub struct MainPodInputs<'a> {
     /// Statements that need to be made public (they can come from input pods or input
     /// statements)
     pub public_statements: &'a [Statement],
+    // TODO: REMOVE THIS
     pub vd_set: VDSet,
 }