feat: add encrypted log outgoing body (#6334)

Fixes #5897, #5900 and #5902.

noir-projects/aztec-nr/aztec/src/encrypted_logs.nr

@@ -1,2 +1,3 @@
 mod header;
 mod incoming_body;
+mod outgoing_body;

noir-projects/aztec-nr/aztec/src/encrypted_logs/outgoing_body.nr

@@ -0,0 +1,110 @@
+use dep::protocol_types::{
+    address::AztecAddress, grumpkin_private_key::GrumpkinPrivateKey, grumpkin_point::GrumpkinPoint,
+    constants::GENERATOR_INDEX__SYMMETRIC_KEY, hash::poseidon2_hash
+};
+
+use dep::std::aes128::aes128_encrypt;
+use dep::std::println;
+
+use crate::keys::point_to_symmetric_key::point_to_symmetric_key;
+
+struct EncryptedLogOutgoingBody {
+    eph_sk: GrumpkinPrivateKey,
+    recipient: AztecAddress,
+    recipient_ivpk_app: GrumpkinPoint,
+}
+
+impl EncryptedLogOutgoingBody {
+    pub fn new(
+        eph_sk: GrumpkinPrivateKey,
+        recipient: AztecAddress,
+        recipient_ivpk_app: GrumpkinPoint
+    ) -> Self {
+        Self { eph_sk, recipient, recipient_ivpk_app }
+    }
+
+    pub fn compute_ciphertext(self, ovsk_app: GrumpkinPrivateKey, eph_pk: GrumpkinPoint) -> [u8; 176] {
+        // Again, we could compute `eph_pk` here, but we keep the interface more similar
+        // and also make it easier to optimise it later as we just pass it along
+
+        let mut buffer: [u8; 160] = [0; 160];
+
+        let serialized_eph_sk: [Field; 2] = self.eph_sk.serialize();
+        let serialized_eph_sk_high = serialized_eph_sk[0].to_be_bytes(32);
+        let serialized_eph_sk_low = serialized_eph_sk[1].to_be_bytes(32);
+
+        let address_bytes = self.recipient.to_field().to_be_bytes(32);
+        let serialized_recipient_ivpk_app = self.recipient_ivpk_app.serialize();
+        let serialized_recipient_ivpk_app_x = serialized_recipient_ivpk_app[0].to_be_bytes(32);
+        let serialized_recipient_ivpk_app_y = serialized_recipient_ivpk_app[1].to_be_bytes(32);
+
+        for i in 0..32 {
+            buffer[i] = serialized_eph_sk_high[i];
+            buffer[i + 32] = serialized_eph_sk_low[i];
+            buffer[i + 64] = address_bytes[i];
+            buffer[i + 96] = serialized_recipient_ivpk_app_x[i];
+            buffer[i + 128] = serialized_recipient_ivpk_app_y[i];
+        }
+
+        // We compute the symmetric key using poseidon.
+        let full_key: [u8; 32] = poseidon2_hash(
+            [
+            ovsk_app.high, ovsk_app.low, eph_pk.x, eph_pk.y,
+            GENERATOR_INDEX__SYMMETRIC_KEY as Field
+        ]
+        ).to_be_bytes(32).as_array();
+
+        let mut sym_key = [0; 16];
+        let mut iv = [0; 16];
+
+        for i in 0..16 {
+            sym_key[i] = full_key[i];
+            iv[i] = full_key[i + 16];
+        }
+        aes128_encrypt(buffer, iv, sym_key).as_array()
+    }
+}
+
+mod test {
+    use crate::encrypted_logs::outgoing_body::EncryptedLogOutgoingBody;
+    use dep::protocol_types::{
+        address::AztecAddress, traits::Empty, constants::GENERATOR_INDEX__NOTE_NULLIFIER,
+        grumpkin_private_key::GrumpkinPrivateKey, grumpkin_point::GrumpkinPoint, hash::poseidon2_hash
+    };
+
+    use crate::context::PrivateContext;
+
+    #[test]
+    fn test_encrypted_log_outgoing_body() {
+        let eph_sk = GrumpkinPrivateKey::new(
+            0x000000000000000000000000000000000f096b423017226a18461115fa8d34bb,
+            0x00000000000000000000000000000000d0d302ee245dfaf2807e604eec4715fe
+        );
+        let recipient_ivsk_app = GrumpkinPrivateKey::new(
+            0x000000000000000000000000000000000f4d97c25d578f9348251a71ca17ae31,
+            0x000000000000000000000000000000004828f8f95676ebb481df163f87fd4022
+        );
+        let sender_ovsk_app = GrumpkinPrivateKey::new(
+            0x00000000000000000000000000000000089c6887cb1446d86c64e81afc78048b,
+            0x0000000000000000000000000000000074d2e28c6bc5176ac02cf7c7d36a444e
+        );
+
+        let eph_pk = eph_sk.derive_public_key();
+        let recipient_ivpk_app = recipient_ivsk_app.derive_public_key();
+
+        let recipient = AztecAddress::from_field(0xdeadbeef);
+
+        let body = EncryptedLogOutgoingBody::new(eph_sk, recipient, recipient_ivpk_app);
+
+        let ciphertext = body.compute_ciphertext(sender_ovsk_app, eph_pk);
+
+        let expected_outgoing_body_ciphertext = [
+            126, 10, 214, 39, 130, 143, 96, 143, 79, 143, 22, 36, 55, 41, 234, 255, 226, 26, 138, 236, 91, 188, 204, 216, 172, 133, 134, 69, 161, 237, 134, 5, 75, 192, 10, 6, 229, 54, 194, 56, 103, 243, 57, 248, 147, 237, 4, 3, 39, 28, 226, 30, 237, 228, 212, 115, 246, 244, 105, 39, 129, 119, 126, 207, 176, 14, 75, 134, 241, 23, 2, 187, 239, 86, 47, 56, 239, 20, 92, 176, 70, 12, 219, 226, 150, 70, 192, 43, 125, 53, 230, 153, 135, 228, 210, 197, 76, 123, 185, 190, 61, 172, 29, 168, 241, 191, 205, 71, 136, 72, 52, 115, 232, 246, 87, 42, 50, 150, 134, 108, 225, 90, 191, 191, 182, 150, 124, 147, 78, 249, 144, 111, 122, 187, 187, 5, 249, 167, 186, 14, 228, 128, 158, 138, 55, 99, 228, 46, 219, 187, 248, 122, 70, 31, 39, 209, 127, 23, 244, 84, 14, 93, 86, 208, 155, 151, 238, 70, 63, 3, 137, 59, 206, 230, 4, 20
+        ];
+
+        for i in 0..expected_outgoing_body_ciphertext.len() {
+            assert_eq(ciphertext[i], expected_outgoing_body_ciphertext[i]);
+        }
+        assert_eq(expected_outgoing_body_ciphertext.len(), ciphertext.len());
+    }
+}

noir-projects/noir-contracts/contracts/test_contract/src/main.nr

@@ -17,6 +17,7 @@ contract Test {
 
     use dep::aztec::encrypted_logs::header::EncryptedLogHeader;
     use dep::aztec::encrypted_logs::incoming_body::EncryptedLogIncomingBody;
+    use dep::aztec::encrypted_logs::outgoing_body::EncryptedLogOutgoingBody;
 
     use dep::aztec::note::constants::MAX_NOTES_PER_PAGE;
 
@@ -377,6 +378,17 @@ contract Test {
         EncryptedLogIncomingBody::new(storage_slot, TestNote::get_note_type_id(), note).compute_ciphertext(secret, point).as_array()
     }
 
+    #[aztec(private)]
+    fn compute_outgoing_log_body_ciphertext(
+        eph_sk: GrumpkinPrivateKey,
+        recipient: AztecAddress,
+        recipient_ivpk_app: GrumpkinPoint,
+        ovsk_app: GrumpkinPrivateKey
+    ) -> [u8; 176] {
+        let eph_pk = eph_sk.derive_public_key();
+        EncryptedLogOutgoingBody::new(eph_sk, recipient, recipient_ivpk_app).compute_ciphertext(ovsk_app, eph_pk)
+    }
+
     #[aztec(public)]
     fn assert_public_global_vars(
         chain_id: Field,

yarn-project/aztec.js/src/index.ts

@@ -125,6 +125,7 @@ export {
   SiblingPath,
   EncryptedLogHeader,
   EncryptedLogIncomingBody,
+  EncryptedLogOutgoingBody,
 } from '@aztec/circuit-types';
 export { NodeInfo } from '@aztec/types/interfaces';
 

yarn-project/circuit-types/src/logs/encrypted_log_outgoing_body.test.ts

@@ -0,0 +1,63 @@
+import { AztecAddress, GrumpkinScalar } from '@aztec/circuits.js';
+import { Grumpkin } from '@aztec/circuits.js/barretenberg';
+import { updateInlineTestData } from '@aztec/foundation/testing';
+
+import { EncryptedLogOutgoingBody } from './encrypted_log_outgoing_body.js';
+
+describe('encrypt log outgoing body', () => {
+  let grumpkin: Grumpkin;
+
+  beforeAll(() => {
+    grumpkin = new Grumpkin();
+  });
+
+  it('encrypt and decrypt a log outgoing body', () => {
+    const ephSk = GrumpkinScalar.random();
+    const recipientIvskApp = GrumpkinScalar.random();
+    const senderOvskApp = GrumpkinScalar.random();
+
+    const ephPk = grumpkin.mul(Grumpkin.generator, ephSk);
+    const recipientIvpkApp = grumpkin.mul(Grumpkin.generator, recipientIvskApp);
+
+    const recipientAddress = AztecAddress.random();
+
+    const body = new EncryptedLogOutgoingBody(ephSk, recipientAddress, recipientIvpkApp);
+
+    const encrypted = body.computeCiphertext(senderOvskApp, ephPk);
+
+    const recreated = EncryptedLogOutgoingBody.fromCiphertext(encrypted, senderOvskApp, ephPk);
+
+    expect(recreated.toBuffer()).toEqual(body.toBuffer());
+  });
+
+  it('encrypt a log outgoing body, generate input for noir test', () => {
+    const ephSk = new GrumpkinScalar(0x0f096b423017226a18461115fa8d34bbd0d302ee245dfaf2807e604eec4715fen);
+    const recipientIvskApp = new GrumpkinScalar(0x0f4d97c25d578f9348251a71ca17ae314828f8f95676ebb481df163f87fd4022n);
+    const senderOvskApp = new GrumpkinScalar(0x089c6887cb1446d86c64e81afc78048b74d2e28c6bc5176ac02cf7c7d36a444en);
+
+    const ephPk = grumpkin.mul(Grumpkin.generator, ephSk);
+    const recipientIvpkApp = grumpkin.mul(Grumpkin.generator, recipientIvskApp);
+
+    const recipientAddress = AztecAddress.fromBigInt(BigInt('0xdeadbeef'));
+
+    const body = new EncryptedLogOutgoingBody(ephSk, recipientAddress, recipientIvpkApp);
+
+    const encrypted = body.computeCiphertext(senderOvskApp, ephPk);
+
+    const recreated = EncryptedLogOutgoingBody.fromCiphertext(encrypted, senderOvskApp, ephPk);
+
+    expect(recreated.toBuffer()).toEqual(body.toBuffer());
+
+    const byteArrayString = `[${encrypted
+      .toString('hex')
+      .match(/.{1,2}/g)!
+      .map(byte => parseInt(byte, 16))}]`;
+
+    // Run with AZTEC_GENERATE_TEST_DATA=1 to update noir test data
+    updateInlineTestData(
+      'noir-projects/aztec-nr/aztec/src/encrypted_logs/outgoing_body.nr',
+      'expected_outgoing_body_ciphertext',
+      byteArrayString,
+    );
+  });
+});

yarn-project/circuit-types/src/logs/encrypted_log_outgoing_body.ts

@@ -0,0 +1,99 @@
+import { AztecAddress, Fr, GeneratorIndex, GrumpkinPrivateKey, Point, type PublicKey } from '@aztec/circuits.js';
+import { Aes128 } from '@aztec/circuits.js/barretenberg';
+import { poseidon2Hash } from '@aztec/foundation/crypto';
+import { BufferReader, serializeToBuffer } from '@aztec/foundation/serialize';
+
+export class EncryptedLogOutgoingBody {
+  constructor(public ephSk: GrumpkinPrivateKey, public recipient: AztecAddress, public recipientIvpkApp: PublicKey) {}
+
+  /**
+   * Serializes the log body
+   *
+   * @returns The serialized log body
+   */
+  public toBuffer(): Buffer {
+    // The serialization of Fq is [high, low] check `grumpkin_private_key.nr`
+    const ephSkBytes = serializeToBuffer([this.ephSk.high, this.ephSk.low]);
+    return serializeToBuffer(ephSkBytes, this.recipient, this.recipientIvpkApp);
+  }
+
+  /**
+   * Deserialized the log body from a buffer
+   *
+   * @param buf - The buffer to deserialize
+   * @returns The deserialized log body
+   */
+  public static fromBuffer(buf: Buffer): EncryptedLogOutgoingBody {
+    const reader = BufferReader.asReader(buf);
+    const high = reader.readObject(Fr);
+    const low = reader.readObject(Fr);
+    const ephSk = GrumpkinPrivateKey.fromHighLow(high, low);
+    const recipient = reader.readObject(AztecAddress);
+    const recipientIvpkApp = reader.readObject(Point); // PublicKey = Point
+
+    return new EncryptedLogOutgoingBody(ephSk, recipient, recipientIvpkApp);
+  }
+
+  /**
+   * Encrypts a log body
+   *
+   * @param ovskApp - The app siloed outgoing viewing secret key
+   * @param ephPk - The ephemeral public key
+   *
+   * @returns The ciphertext of the encrypted log body
+   */
+  public computeCiphertext(ovskApp: GrumpkinPrivateKey, ephPk: PublicKey) {
+    // We could use `ephSk` and compute `ephPk` from it.
+    // We mainly provide it to keep the same api and potentially slight optimization as we can reuse it.
+
+    const aesSecret = EncryptedLogOutgoingBody.derivePoseidonAESSecret(ovskApp, ephPk);
+
+    const key = aesSecret.subarray(0, 16);
+    const iv = aesSecret.subarray(16, 32);
+
+    const aes128 = new Aes128();
+    const buffer = this.toBuffer();
+
+    return aes128.encryptBufferCBC(buffer, iv, key);
+  }
+
+  /**
+   * Decrypts a log body
+   *
+   * @param ciphertext - The ciphertext buffer
+   * @param ovskApp - The app siloed outgoing viewing secret key
+   * @param ephPk - The ephemeral public key
+   *
+   * @returns The decrypted log body
+   */
+  public static fromCiphertext(
+    ciphertext: Buffer | bigint[],
+    ovskApp: GrumpkinPrivateKey,
+    ephPk: PublicKey,
+  ): EncryptedLogOutgoingBody {
+    const input = Buffer.isBuffer(ciphertext) ? ciphertext : Buffer.from(ciphertext.map((x: bigint) => Number(x)));
+
+    const aesSecret = EncryptedLogOutgoingBody.derivePoseidonAESSecret(ovskApp, ephPk);
+    const key = aesSecret.subarray(0, 16);
+    const iv = aesSecret.subarray(16, 32);
+
+    const aes128 = new Aes128();
+    const buffer = aes128.decryptBufferCBC(input, iv, key);
+
+    return EncryptedLogOutgoingBody.fromBuffer(buffer);
+  }
+
+  /**
+   * Derives an AES symmetric key from the app siloed outgoing viewing secret key
+   * and the ephemeral public key using poseidon.
+   *
+   * @param ovskApp - The app siloed outgoing viewing secret key
+   * @param ephPk - The ephemeral public key
+   * @returns
+   */
+  static derivePoseidonAESSecret(ovskApp: GrumpkinPrivateKey, ephPk: PublicKey) {
+    // For performance reasons, we do NOT use the usual `deriveAESSecret` function here
+    // Instead we compute the using using poseidon
+    return poseidon2Hash([ovskApp.high, ovskApp.low, ephPk.x, ephPk.y, GeneratorIndex.SYMMETRIC_KEY]).toBuffer();
+  }
+}

yarn-project/circuit-types/src/logs/index.ts

@@ -12,3 +12,4 @@ export * from './unencrypted_l2_log.js';
 export * from './extended_unencrypted_l2_log.js';
 export * from './encrypted_log_header.js';
 export * from './encrypted_log_incoming_body.js';
+export * from './encrypted_log_outgoing_body.js';

yarn-project/end-to-end/src/e2e_encryption.test.ts

@@ -1,4 +1,13 @@
-import { EncryptedLogHeader, EncryptedLogIncomingBody, Fr, GrumpkinScalar, Note, type Wallet } from '@aztec/aztec.js';
+import {
+  AztecAddress,
+  EncryptedLogHeader,
+  EncryptedLogIncomingBody,
+  EncryptedLogOutgoingBody,
+  Fr,
+  GrumpkinScalar,
+  Note,
+  type Wallet,
+} from '@aztec/aztec.js';
 import { Aes128, Grumpkin } from '@aztec/circuits.js/barretenberg';
 import { TestContract } from '@aztec/noir-contracts.js';
 
@@ -99,4 +108,27 @@ describe('e2e_encryption', () => {
 
     expect(recreated.toBuffer()).toEqual(body.toBuffer());
   });
+
+  it('encrypts log outgoing body', async () => {
+    const ephSk = GrumpkinScalar.random();
+    const recipientIvskApp = GrumpkinScalar.random();
+    const senderOvskApp = GrumpkinScalar.random();
+
+    const ephPk = grumpkin.mul(Grumpkin.generator, ephSk);
+    const recipientIvpkApp = grumpkin.mul(Grumpkin.generator, recipientIvskApp);
+
+    const recipientAddress = AztecAddress.fromBigInt(BigInt('0xdeadbeef'));
+
+    const body = new EncryptedLogOutgoingBody(ephSk, recipientAddress, recipientIvpkApp);
+
+    const encrypted = await contract.methods
+      .compute_outgoing_log_body_ciphertext(ephSk, recipientAddress, recipientIvpkApp, senderOvskApp)
+      .simulate();
+
+    expect(Buffer.from(encrypted.map((x: bigint) => Number(x)))).toEqual(body.computeCiphertext(senderOvskApp, ephPk));
+
+    const recreated = EncryptedLogOutgoingBody.fromCiphertext(encrypted, senderOvskApp, ephPk);
+
+    expect(recreated.toBuffer()).toEqual(body.toBuffer());
+  });
 });