feat: add self-encryption support

package.json

@@ -84,7 +84,8 @@
   },
   "dependencies": {
     "@noble/secp256k1": "^1.5.2",
-    "@xmtp/proto": "^3.29.0",
+    "@xmtp/ecies-bindings-wasm": "^0.1.5",
+    "@xmtp/proto": "^3.28.0-beta.1",
     "async-mutex": "^0.4.0",
     "elliptic": "^6.5.4",
     "ethers": "^5.5.3",

src/crypto/SelfEncryption.ts

@@ -0,0 +1,32 @@
+import {
+  // eslint-disable-next-line camelcase
+  ecies_decrypt_k256_sha3_256,
+  // eslint-disable-next-line camelcase
+  ecies_encrypt_k256_sha3_256,
+} from '@xmtp/ecies-bindings-wasm'
+import { PrivateKey } from '.'
+
+// Uses ECIES to encrypt messages where the sender and recipient are the same
+export default class SelfEncryption {
+  privateKey: PrivateKey
+
+  constructor(identityKey: PrivateKey) {
+    this.privateKey = identityKey
+  }
+
+  encrypt(data: Uint8Array): Uint8Array {
+    return ecies_encrypt_k256_sha3_256(
+      this.privateKey.publicKey.secp256k1Uncompressed.bytes,
+      this.privateKey.secp256k1.bytes,
+      data
+    )
+  }
+
+  decrypt(message: Uint8Array): Uint8Array {
+    return ecies_decrypt_k256_sha3_256(
+      this.privateKey.publicKey.secp256k1Uncompressed.bytes,
+      this.privateKey.secp256k1.bytes,
+      message
+    )
+  }
+}

test/crypto/P4Encryption.test.ts

@@ -0,0 +1,36 @@
+import { PrivateKeyBundleV1 } from '../../src/crypto/PrivateKeyBundle'
+import SelfEncryption from '../../src/crypto/SelfEncryption'
+import { newWallet } from '../helpers'
+import { equalBytes } from '../../src/crypto/utils'
+
+describe('SelfEncryption', () => {
+  let bundle: PrivateKeyBundleV1
+
+  beforeEach(async () => {
+    bundle = await PrivateKeyBundleV1.generate(newWallet())
+  })
+
+  it('round trips data', async () => {
+    const message = new TextEncoder().encode('hello world')
+    const encryptor = new SelfEncryption(bundle.identityKey)
+
+    const ciphertext = encryptor.encrypt(message)
+    expect(ciphertext).toBeDefined()
+
+    const decrypted = encryptor.decrypt(ciphertext)
+    expect(equalBytes(decrypted, message)).toBeTruthy()
+  })
+
+  it('throws on decryption failure', async () => {
+    const message = new TextEncoder().encode('hello world')
+    const encryptor = new SelfEncryption(bundle.identityKey)
+
+    const ciphertext = encryptor.encrypt(message)
+    expect(ciphertext).toBeDefined()
+
+    const differentEncryptor = new SelfEncryption(
+      (await PrivateKeyBundleV1.generate(newWallet())).identityKey
+    )
+    expect(() => differentEncryptor.decrypt(ciphertext)).toThrow()
+  })
+})