Function decryptData

frontend/src/utils/crypto.ts:85–115

(
  encryptedBase64: string,
  password: string,
)

 * Returns the parsed JSON data.
 */
export async function decryptData(
  encryptedBase64: string,
  password: string,
): Promise<any> {
  try {
    const binary = atob(encryptedBase64);
    const combined = new Uint8Array(binary.length);
    for (let i = 0; i < binary.length; i++) {
      combined[i] = binary.charCodeAt(i);
    }

    const salt = combined.subarray(0, SALT_LENGTH);
    const iv = combined.subarray(SALT_LENGTH, SALT_LENGTH + IV_LENGTH);
    const encryptedBytes = combined.subarray(SALT_LENGTH + IV_LENGTH);

    const passwordKey = await getPasswordKey(password);
    const aesKey = await deriveKey(passwordKey, salt);

    const decryptedContent = await crypto.subtle.decrypt(
      { name: "AES-GCM", iv: iv },
      aesKey,
      encryptedBytes,
    );

    const dec = new TextDecoder();
    const jsonStr = dec.decode(decryptedContent);
    return JSON.parse(jsonStr);
  } catch (e) {
    throw new Error("Decryption failed. Incorrect password or corrupted data.");
  }
}