circuits: remove elgamal encryption

circuits/CHANGELOG.md

@@ -21,6 +21,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Rename `skeleton_hash` to `payload_hash` [#188]
 - Make `TxCircuit` to use the Recipient gadget
 
+### Removed
+
+- Remove `RecipientParameters`
+- Remove `elgamal::encrypt` and `elgamal::decrypt`
+
 ## [0.1.0] - 2024-05-22
 
 ### Added

circuits/src/encryption/elgamal.rs

@@ -9,38 +9,9 @@
 //!
 //! Reference: https://link.springer.com/chapter/10.1007/3-540-39568-7_2
 
-use dusk_jubjub::{JubJubExtended, JubJubScalar, GENERATOR};
+use dusk_jubjub::{JubJubScalar, GENERATOR};
 use dusk_plonk::prelude::*;
 
-/// Encrypts a JubJubExtended plaintext given a public key and a fresh random
-/// number 'r'.
-///
-/// ## Return
-/// Returns a ciphertext (JubJubExtended, JubJubExtended).
-pub fn encrypt(
-    public_key: &JubJubExtended,
-    plaintext: &JubJubExtended,
-    r: &JubJubScalar,
-) -> (JubJubExtended, JubJubExtended) {
-    let ciphertext_1 = GENERATOR * r;
-    let ciphertext_2 = plaintext + public_key * r;
-
-    (ciphertext_1, ciphertext_2)
-}
-
-/// Decrypts a ciphertext given a secret key.
-///
-/// ## Return
-/// Returns a JubJubExtended plaintext.
-pub fn decrypt(
-    secret_key: &JubJubScalar,
-    ciphertext_1: &JubJubExtended,
-    ciphertext_2: &JubJubExtended,
-) -> JubJubExtended {
-    // return the plaintext
-    ciphertext_2 - ciphertext_1 * secret_key
-}
-
 /// Encrypt in-circuit a plaintext WitnessPoint.
 ///
 /// ## Return

circuits/src/lib.rs

@@ -16,8 +16,5 @@ mod recipient;
 /// Transaction structs, and circuit
 pub mod transaction;
 
-/// Recipient Parameters
-pub use recipient::RecipientParameters;
-
 /// ElGamal asymmetric cipher
 pub use encryption::elgamal;

circuits/src/recipient.rs

@@ -6,123 +6,11 @@
 
 #![allow(non_snake_case)]
 
-use dusk_jubjub::JubJubScalar;
 use dusk_plonk::prelude::*;
-use ff::Field;
-use jubjub_schnorr::{gadgets, SecretKey as SchnorrSecretKey, Signature};
-use rand::{CryptoRng, RngCore};
+use jubjub_schnorr::gadgets;
+use phoenix_core::RecipientParameters;
 
 use crate::elgamal;
-use phoenix_core::{PublicKey, SecretKey};
-
-const TX_OUTPUT_NOTES: usize = 2;
-
-/// Parameters needed to prove a recipient in-circuit
-#[derive(Debug, Clone, Copy)]
-pub struct RecipientParameters {
-    /// Public key of the transaction sender
-    pub sender_pk: PublicKey,
-    /// Note public keys of each note recipient
-    pub output_npk: [JubJubAffine; TX_OUTPUT_NOTES],
-    /// Signatures of 'payload_hash' verifiable using 'pk_A' and 'pk_B'
-    pub sig: [Signature; TX_OUTPUT_NOTES],
-    /// Asymmetric encryption of 'pk_A' using both recipients 'npk'
-    pub enc_A: [(JubJubExtended, JubJubExtended); TX_OUTPUT_NOTES],
-    /// Asymmetric encryption of 'pk_B' using both recipients 'npk'
-    pub enc_B: [(JubJubExtended, JubJubExtended); TX_OUTPUT_NOTES],
-    /// Randomness needed to encrypt/decrypt 'pk_A'
-    pub r_A: [JubJubScalar; TX_OUTPUT_NOTES],
-    /// Randomness needed to encrypt/decrypt 'pk_B'
-    pub r_B: [JubJubScalar; TX_OUTPUT_NOTES],
-}
-
-impl Default for RecipientParameters {
-    fn default() -> Self {
-        let sk =
-            SecretKey::new(JubJubScalar::default(), JubJubScalar::default());
-        let sender_pk = PublicKey::from(&sk);
-
-        Self {
-            sender_pk,
-            output_npk: [JubJubAffine::default(), JubJubAffine::default()],
-            sig: [Signature::default(), Signature::default()],
-            enc_A: [(JubJubExtended::default(), JubJubExtended::default());
-                TX_OUTPUT_NOTES],
-            enc_B: [(JubJubExtended::default(), JubJubExtended::default());
-                TX_OUTPUT_NOTES],
-            r_A: [JubJubScalar::default(); TX_OUTPUT_NOTES],
-            r_B: [JubJubScalar::default(); TX_OUTPUT_NOTES],
-        }
-    }
-}
-
-impl RecipientParameters {
-    /// Create the recipient parameter
-    pub fn new(
-        rng: &mut (impl RngCore + CryptoRng),
-        sender_sk: &SecretKey,
-        output_npk: [JubJubAffine; TX_OUTPUT_NOTES],
-        payload_hash: BlsScalar,
-    ) -> Self {
-        // Encrypt the public key of the sender. We need to encrypt
-        // both 'A' and 'B', using both tx output note public keys.
-        let sender_pk = PublicKey::from(sender_sk);
-
-        let r_A = [
-            JubJubScalar::random(&mut *rng),
-            JubJubScalar::random(&mut *rng),
-        ];
-        let r_B = [
-            JubJubScalar::random(&mut *rng),
-            JubJubScalar::random(&mut *rng),
-        ];
-
-        let (A_enc_1_c1, A_enc_1_c2) = elgamal::encrypt(
-            &output_npk[0].into(), // note_pk_1.as_ref(),
-            sender_pk.A(),
-            &r_A[0],
-        );
-
-        let (B_enc_1_c1, B_enc_1_c2) = elgamal::encrypt(
-            &output_npk[0].into(), // note_pk_1.as_ref(),
-            sender_pk.B(),
-            &r_B[0],
-        );
-        let (A_enc_2_c1, A_enc_2_c2) = elgamal::encrypt(
-            &output_npk[1].into(), // note_pk_2.as_ref(),
-            sender_pk.A(),
-            &r_A[1],
-        );
-
-        let (B_enc_2_c1, B_enc_2_c2) = elgamal::encrypt(
-            &output_npk[1].into(), // note_pk_2.as_ref(),
-            sender_pk.B(),
-            &r_B[1],
-        );
-
-        let enc_A = [(A_enc_1_c1, A_enc_1_c2), (A_enc_2_c1, A_enc_2_c2)];
-        let enc_B = [(B_enc_1_c1, B_enc_1_c2), (B_enc_2_c1, B_enc_2_c2)];
-
-        // Sign the payload hash using both 'a' and 'b'
-        let schnorr_sk_a = SchnorrSecretKey::from(sender_sk.a());
-        let sig_A = schnorr_sk_a.sign(rng, payload_hash);
-
-        let schnorr_sk_b = SchnorrSecretKey::from(sender_sk.b());
-        let sig_B = schnorr_sk_b.sign(rng, payload_hash);
-
-        let sig = [sig_A, sig_B];
-
-        RecipientParameters {
-            sender_pk,
-            output_npk,
-            sig,
-            enc_A,
-            enc_B,
-            r_A,
-            r_B,
-        }
-    }
-}
 
 /// Gadget to prove a valid origin for a given transaction.
 pub(crate) fn gadget(

circuits/src/transaction.rs

@@ -19,9 +19,11 @@ use rand::{CryptoRng, RngCore, SeedableRng};
 extern crate alloc;
 use alloc::vec::Vec;
 
-use phoenix_core::{Error as PhoenixError, Note, SecretKey, ViewKey};
+use phoenix_core::{
+    Error as PhoenixError, Note, RecipientParameters, SecretKey, ViewKey,
+};
 
-use crate::{recipient, recipient::RecipientParameters};
+use crate::recipient;
 
 const TX_OUTPUT_NOTES: usize = 2;
 

circuits/tests/elgamal.rs

@@ -7,8 +7,8 @@
 use dusk_jubjub::{JubJubAffine, JubJubScalar, GENERATOR_EXTENDED};
 use dusk_plonk::prelude::*;
 use ff::Field;
-use phoenix_circuits::elgamal;
-use phoenix_core::{PublicKey, SecretKey};
+use phoenix_circuits::elgamal::{decrypt_gadget, encrypt_gadget};
+use phoenix_core::{elgamal, PublicKey, SecretKey};
 use rand::rngs::StdRng;
 use rand::SeedableRng;
 
@@ -77,19 +77,15 @@ impl Circuit for ElGamalCircuit {
 
         // ENCRYPT
         let (ciphertext_1, ciphertext_2) =
-            elgamal::encrypt_gadget(composer, public_key, plaintext, r)?;
+            encrypt_gadget(composer, public_key, plaintext, r)?;
 
         // ASSERT RESULT MAKING THE CIPHERTEXT PUBLIC
         composer.assert_equal_public_point(ciphertext_1, self.ciphertext_1);
         composer.assert_equal_public_point(ciphertext_2, self.ciphertext_2);
 
         // DECRYPT
-        let dec_plaintext = elgamal::decrypt_gadget(
-            composer,
-            secret_key,
-            ciphertext_1,
-            ciphertext_2,
-        );
+        let dec_plaintext =
+            decrypt_gadget(composer, secret_key, ciphertext_1, ciphertext_2);
 
         // ASSERT RESULTING PLAINTEXT
         composer.assert_equal_point(dec_plaintext, plaintext);

circuits/tests/transaction.rs

@@ -13,11 +13,10 @@ use dusk_plonk::prelude::*;
 use ff::Field;
 use poseidon_merkle::{Item, Tree};
 
-use phoenix_circuits::{
-    transaction::{TxCircuit, TxInputNote, TxOutputNote},
-    RecipientParameters,
+use phoenix_circuits::transaction::{TxCircuit, TxInputNote, TxOutputNote};
+use phoenix_core::{
+    value_commitment, Note, PublicKey, RecipientParameters, SecretKey,
 };
-use phoenix_core::{value_commitment, Note, PublicKey, SecretKey};
 
 #[macro_use]
 extern crate lazy_static;