CupCake

Here's a comprehensive overview of Cake Wallet's Cupcake feature:

What is Cupcake?

Cupcake is a companion app in the Cake Wallet family that turns an old phone into an air-gapped hardware wallet — no need to buy a $200+ dedicated hardware device or wait weeks for shipping. You install it on a spare phone (or tablet), and it acts as a dedicated offline signer that keeps your private keys completely isolated from the internet ^[1].

How It Works

The architecture splits responsibilities between two devices:

• Cupcake (offline device): Holds the private keys and signs transactions. It has all network permissions disabled at the OS level, so it physically cannot connect to the internet ^[2].
• Cake Wallet (online device): Holds only view keys / public keys, letting you see balances, transaction history, and initiate new transactions ^[1:1].

Transaction Flow via Animated QR Codes

Since Cupcake is air-gapped, transactions are signed using animated QR codes:

1. You initiate a transaction in Cake Wallet (enter address, amount, etc.).
2. Instead of a "send" button, Cake Wallet displays an animated QR code containing the unsigned transaction.
3. You scan that QR code with the Cupcake device, which displays the full transaction details for you to review and approve.
4. Cupcake signs the transaction and displays its own animated QR code containing only the signed transaction — no private keys are ever shared.
5. You scan that back into Cake Wallet, which broadcasts the signed transaction to the network.

^[2:1]

Security Model

Cupcake leverages the best security features of the device it runs on:

• Secure Enclave storage: On devices like Google Pixels and iPhones, private keys are stored in the secure enclave, preventing other apps from accessing them ^[2:2].
• PIN brute-force protection: The secure enclave enforces PIN limits, so an attacker with physical access to the phone can't easily brute-force the PIN. Breaking this would require breaking the phone's entire security model ^[2:3].
• Encrypted wallet file: The wallet file is encrypted with a key derived from both your PIN/password and a component generated by the secure enclave — so even if the phone's storage is captured, the wallet remains protected ^[2:4].
• Proof-of-work fallback: For older devices without a secure enclave, Cupcake implements a novel proof-of-work mechanism that makes each failed PIN attempt progressively harder, defending against evil-maid and opportunistic attacks ^[2:5].
• App signing security: OS-level app signing ensures that even if tricked into installing a malicious version, it cannot overwrite the legitimate app ^[2:6].

Supported Cryptocurrencies

^[1:2]

Platform Availability

Cupcake is available on both iOS and Android ^[1:3][3].

Getting Started (5 Steps, ~5 Minutes)

1. Download Cupcake on a spare device
2. Turn off internet on that device for best security
3. Create your wallet and write down your seed phrase
4. Set up view-only access in your main Cake Wallet
5. Start using hardware-level security immediately

^[4]

Handling Updates

Since the device is kept offline, updates can be handled two ways:

• Standard approach: Briefly allow the device online for official OS and app updates (Cupcake's lack of network permissions keeps keys safe) ^[2:7].
• Paranoid approach: Keep the device permanently offline and manually transfer update files (e.g., APKs via flash drive). This works mainly on Android due to Apple's side-loading restrictions ^[2:8].

In summary, Cupcake democratizes hardware-wallet-grade security by repurposing an old phone as an air-gapped, offline transaction signer that pairs with Cake Wallet through QR codes — giving you the security benefits of a dedicated hardware wallet without the cost or wait.

References

1. Cupcake | Cake Wallet - Docs (25%) ↩︎ ↩︎ ↩︎ ↩︎
2. How Cupcake Actually Works: A Technical Deep(ish) Dive (71%) ↩︎ ↩︎ ↩︎ ↩︎ ↩︎ ↩︎ ↩︎ ↩︎ ↩︎
3. Cupcake: Security, Made Easy - Apps on Google Play (2%) ↩︎
4. Meet Cupcake: Your New Secret Weapon for Crypto Security (2%) ↩︎