Zukka Private Secure Messenger

Setting Up Without a Phone Number

Opening Zukka for the first time presents a registration screen that asks for three things: a nickname, a master password, and an encryption phrase. No phone number field. No email field. No SMS verification code. The app does not ask for access to your contacts. It does not request permission to read your device storage. It does not ask for location data. You type in a nickname that will be visible to people you invite, but it is not searchable by anyone else. The master password is used to log in. The encryption phrase is the key to your messages. The app warns you upfront: if you lose that phrase, your data is gone forever. There is no reset email, no security questions, no support backdoor. That warning appears before you even create an account. The registration process takes about two minutes. No personal information is collected. No profile is built. No advertising ID is tied to your account.

After registration, the app generates a default invite code. This is a 16-digit number, like 2612-0614-3022-4817. You can share this code with anyone you want to connect with. They install Zukka, enter the code, and become your contact. The app does not store a list of your contacts on your device. It does not scan your phone for other Zukka users. Every connection is initiated by you, through an invite you create. You can set limits on each invite: how many people can use it, and for how long it remains active. You can revoke an invite at any time. When you revoke it, people who already used it keep talking to you. Only new people trying to use the code are locked out. This is a deliberate design choice. The invite is the door, not the relationship. Changing the door does not affect the people already inside.

How the Split Key and Stateless Storage Actually Work

The encryption system is built around a split key. Your encryption phrase generates a key that is divided into two halves. One half is stored on the server. The other half is stored on your device. Neither half can decrypt anything on its own. Only when you type your encryption phrase does the app combine the two halves and unlock your conversations. The server holds only ciphertext — encrypted blobs that it has no keys to open. If the server's database is leaked, the attacker gets only unreadable data. They cannot get your key, and they cannot read your messages. This is a different model from most messaging apps. Signal stores your message history on your device. Telegram stores it on the server but can read it if they choose. Zukka stores nothing on your device and holds no keys on the server. The trade-off is that if you lose your phrase, there is no recovery. The app states this clearly: "That isn't a flaw — it's the price of nobody else being able to open it either."

The stateless design means your phone never writes messages to storage. When you open a conversation, the app downloads encrypted messages from the server, decrypts them locally on your screen, and displays them. When you close the app, the decrypted content is gone. Your phone holds no message history, no photo archive, no readable contact list. If your phone is lost, stolen, or seized, there is no history to scroll through. The device does hold one half of the encryption key, but that half is useless without your phrase and the server half. The app also offers a remote kill feature: you can destroy the server's half of the key, after which nothing tied to that account can ever be decrypted again. This is designed for situations where a device is out of your hands and you want to ensure that even the encrypted data becomes permanently inaccessible.

Real Performance, Calls, and the Circle Plan

Voice and video calls are encrypted end-to-end. The app supports one-to-one calls and group calls. Group chats can have up to 20 members. Each conversation uses its own encryption key. The app also supports photos, videos, files, voice notes, and location sharing. Before any photo or document is encrypted and sent, the app strips hidden metadata — GPS coordinates, author names, timestamps. This happens automatically. You do not need to enable it. The app does not show ads. There are no tracking pixels, no analytics scripts, no third-party SDKs for advertising. The app is funded by subscriptions. The base plan costs $8.99 per month. The Circle plan allows you to invite up to 30 people to use Zukka for free. Those guests get the full experience — encrypted chats, calls, files — but they cannot create their own invites or build their own network. They exist to talk with the people who sponsored them. If a guest wants their own network, they can take a paid plan.

The app runs on Android 8.0 and newer. It does not require Google Mobile Services. It works on de-Googled Android systems like GrapheneOS, /e/OS, and LineageOS. On devices without Google services, the app maintains its own encrypted connection to deliver messages and calls in real time. The official website notes that this uses a little more battery, but it keeps Google out of the loop. The app is available on Google Play and as a direct APK download from the official site. The APK comes with a published SHA-256 checksum so you can verify the file before installing. The app is also planned for iOS, but that version is not yet available. The current focus is Android.

Storage Behavior and the Master Mode Option

The default storage mode is blind storage: the server holds ciphertext, the device holds nothing. For users who do not want their data — even encrypted — living on the app's servers, there is a Master mode. This requires a second device that you own, kept somewhere safe with a good internet connection. That second device becomes the vault that holds all your data: contacts, messages, files. Your everyday phone holds nothing, as always. The app's server becomes a blind courier: it relays requests from your phone to your master device, and relays answers back. Your data never lives on the app's infrastructure, even in encrypted form. This mode is planned for launch. A further option, self-hosted, is on the roadmap: a ready-made package that runs the entire Zukka backend on your own server, for a fully autonomous closed network. In that scenario, the app company is no longer part of the picture at all. The trade-off is that it connects only your own group.

The app supports multiple accounts on the same device. Each account is protected by a different PIN. This is designed for plausible deniability. If someone forces you to unlock the app, you give them the PIN of an everyday account. They see that account, they believe you cooperated, and the conversation ends. The app does not have a limit on the number of accounts, so there is no way to tell if a person has one account or several. There is also a panic password: a separate password you configure in advance. When entered at login, it destroys the data. There is no undo. The app states this clearly when you set it up. The app also allows per-contact notification sounds and ringtones, so you can know who is calling without looking at the screen.