1 files changed, 93 insertions, 0 deletions
diff --git a/packages/excalidraw/data/encryption.ts b/packages/excalidraw/data/encryption.ts
new file mode 100644
index 0000000..33e6899
--- /dev/null
+++ b/packages/excalidraw/data/encryption.ts
@@ -0,0 +1,93 @@
+import { ENCRYPTION_KEY_BITS } from "../constants";
+import { blobToArrayBuffer } from "./blob";
+
+export const IV_LENGTH_BYTES = 12;
+
+export const createIV = () => {
+  const arr = new Uint8Array(IV_LENGTH_BYTES);
+  return window.crypto.getRandomValues(arr);
+};
+
+export const generateEncryptionKey = async <
+  T extends "string" | "cryptoKey" = "string",
+>(
+  returnAs?: T,
+): Promise<T extends "cryptoKey" ? CryptoKey : string> => {
+  const key = await window.crypto.subtle.generateKey(
+    {
+      name: "AES-GCM",
+      length: ENCRYPTION_KEY_BITS,
+    },
+    true, // extractable
+    ["encrypt", "decrypt"],
+  );
+  return (
+    returnAs === "cryptoKey"
+      ? key
+      : (await window.crypto.subtle.exportKey("jwk", key)).k
+  ) as T extends "cryptoKey" ? CryptoKey : string;
+};
+
+export const getCryptoKey = (key: string, usage: KeyUsage) =>
+  window.crypto.subtle.importKey(
+    "jwk",
+    {
+      alg: "A128GCM",
+      ext: true,
+      k: key,
+      key_ops: ["encrypt", "decrypt"],
+      kty: "oct",
+    },
+    {
+      name: "AES-GCM",
+      length: ENCRYPTION_KEY_BITS,
+    },
+    false, // extractable
+    [usage],
+  );
+
+export const encryptData = async (
+  key: string | CryptoKey,
+  data: Uint8Array | ArrayBuffer | Blob | File | string,
+): Promise<{ encryptedBuffer: ArrayBuffer; iv: Uint8Array }> => {
+  const importedKey =
+    typeof key === "string" ? await getCryptoKey(key, "encrypt") : key;
+  const iv = createIV();
+  const buffer: ArrayBuffer | Uint8Array =
+    typeof data === "string"
+      ? new TextEncoder().encode(data)
+      : data instanceof Uint8Array
+      ? data
+      : data instanceof Blob
+      ? await blobToArrayBuffer(data)
+      : data;
+
+  // We use symmetric encryption. AES-GCM is the recommended algorithm and
+  // includes checks that the ciphertext has not been modified by an attacker.
+  const encryptedBuffer = await window.crypto.subtle.encrypt(
+    {
+      name: "AES-GCM",
+      iv,
+    },
+    importedKey,
+    buffer as ArrayBuffer | Uint8Array,
+  );
+
+  return { encryptedBuffer, iv };
+};
+
+export const decryptData = async (
+  iv: Uint8Array,
+  encrypted: Uint8Array | ArrayBuffer,
+  privateKey: string,
+): Promise<ArrayBuffer> => {
+  const key = await getCryptoKey(privateKey, "decrypt");
+  return window.crypto.subtle.decrypt(
+    {
+      name: "AES-GCM",
+      iv,
+    },
+    key,
+    encrypted,
+  );
+};