feat: ecdh encrypt

src/util_ecdh.rs

@@ -0,0 +1,34 @@
+use p256::ecdh::EphemeralSecret;
+use rand::rngs::OsRng;
+use rust_util::{opt_result, XResult};
+
+use p256::pkcs8::EncodePublicKey;
+use p256::{EncodedPoint, PublicKey};
+use p256::elliptic_curve::sec1::{FromEncodedPoint, ToEncodedPoint};
+
+#[derive(Debug)]
+pub struct EphemeralKeyBytes(EncodedPoint);
+
+impl EphemeralKeyBytes {
+    pub fn from_public_key(epk: &PublicKey) -> Self {
+        EphemeralKeyBytes(epk.to_encoded_point(true))
+    }
+
+    pub fn decompress(&self) -> EncodedPoint {
+        // EphemeralKeyBytes is a valid compressed encoding by construction.
+        let p = PublicKey::from_encoded_point(&self.0).unwrap();
+        p.to_encoded_point(false)
+    }
+}
+
+pub fn compute_shared_secret(public_key_point_hex: &str) -> XResult<(Vec<u8>, Vec<u8>)> {
+    let public_key_point_bytes = opt_result!(hex::decode(public_key_point_hex), "Parse public key point hex failed: {}");
+    let encoded_point = opt_result!(EncodedPoint::from_bytes(&public_key_point_bytes), "Parse public key point failed: {}");
+    let public_key = PublicKey::from_encoded_point(&encoded_point).unwrap();
+
+    let esk = EphemeralSecret::random(&mut OsRng);
+    let epk = esk.public_key();
+    let shared_secret = esk.diffie_hellman(&public_key);
+    let epk_public_key_der = opt_result!(epk.to_public_key_der(), "Convert epk to SPKI failed: {}");
+    Ok((shared_secret.raw_secret_bytes().as_slice().to_vec(), epk_public_key_der.to_vec()))
+}