Bennu Bitcoin Wallet: Machankura’s New Group Wallet Lives Inside an Encrypted Chat
Machankura has announced Bennu, an experimental open-source wallet where the group chat is the wallet. No single person or phone ever holds the full key.
Machankura, the project behind Bitcoin for feature phones, has announced Bennu at bennu.8333.mobi. The Bennu Bitcoin wallet runs on Android, iOS and desktop. Chat isn’t an add-on here. It’s the main screen. Members talk about a payment and sign it in the same encrypted conversation.
How It Works
- Set Up a Profile: A 12-word recovery phrase is generated locally on your device to create both your chat and wallet keys. Alternatively, you can import an existing Nostr key.
Start a Group: All messages are end-to-end encrypted and routed over customizable Nostr relays.
Generate the Shared Key: Group members perform a “key ceremony” directly within the chat. Each device contributes its own secret key share without revealing it to others. Using FROST (a threshold signature scheme), the process generates a threshold key (e.g., 2-of-4 multisig), ensuring the full key never exists in a single location.
Spend Collectively: Any member can propose a payment inside the chat. Each device verifies the transaction details before signing. Once the required threshold of signatures is reached, the transaction is broadcast.
Track Funds Transparently: All members can view the wallet’s balance and transaction history. Non-signing members, or external software like Bitcoin Core, can track activity using standard wallet descriptors.
On the blockchain, these group payments appear as standard, single-key Taproot transactions, preserving privacy and minimizing fees.
Hierarchical Groups & Guardian Recovery
Parent groups can create child groups, each equipped with its own chat, key ceremony, and wallet addresses. A child group’s keys are completely independent of its parent’s. To establish hierarchy, the parent group’s signers sign a publicly verifiable “birth certificate,” though this gives the parent no authority to sign routine transactions on the child’s behalf. This architecture is partially inspired by mantra.press.
Groups can also serve as guardians. A guardian receives a delayed spending path secured by a timelock measured in block height. Bennu supports delays ranging from 6 to 65,535 blocks (with a default setting of approximately two hours). Under normal conditions, this key remains untouched; it exists solely so a parent group or guardian can recover funds if a child group loses access or becomes unreachable. Because this recovery mechanism relies on a hidden Taproot branch, utilizing it incurs only a marginal fee increase over a standard transaction.
This safeguard also extends to individual users: you can manage a single-user wallet for daily spending while designating a trusted group to serve as a recovery guardian.
Why This Matters for Africa
Founded by Kgothatso Ngako, Machankura built its reputation by making Bitcoin accessible in areas with limited smartphone and internet access. Its USSD and SMS service connects feature-phone users across countries like Ghana, Kenya, Malawi, Namibia, Nigeria, South Africa, Uganda, and Zambia. While its earlier “Clans” feature enabled shared approvals for Lightning transactions, Bennu extends this model to self-custodial, on-chain Bitcoin transactions.
Bennu is tailored for existing financial collectives like stokvels, chamas, family savings groups, and small organizations. However, unlike Machankura’s USSD tool, Bennu is a full application requiring a smartphone or desktop computer.
Important Considerations Before Use
It Is Experimental: Only deposit funds you are willing to risk.
Non-Custodial Design: Bennu does not host accounts or store key shares on central servers. Security relies entirely on standard client integrity and the underlying Bitcoin network.
Early Access: Testing is ongoing. An Android APK is available, while TestFlight and Google Play access can be unlocked with a nominal on-chain payment.
Establish Guardian Terms Early: Because a guardian can sweep funds once the block-delay expires, group rules and recovery conditions must be clearly agreed upon before funding the wallet.
Unproven Architecture: The design requires further real-world testing regarding client synchronization, key ceremonies, and recovery pathways.
The codebase is hosted on GitHub, with official updates shared on X. The Bennu logo features a stylized heron—a reference to the ancient Egyptian Bennu bird.