Quite simply: no one but you. Not us, not your ISP, not a hacker, and not a government agency. As long as you keep your password safe, and your password is reasonably strong, then you are the only person in the world with the ability to decrypt your notes.
How? When you use any of the Standard Notes applications, whether on your desktop or on your phone, any change you make is immediately encrypted on your device in a secure offline environment, then synced to your other devices, where it is then decrypted in the same secure environment. This means the actual plain text contents of your notes never leave your devices, and are thus incapable of being intercepted or read by anyone else.
For more on how we handle your privacy and security, check out our easy to read Privacy Manifesto.