Authenticated card flow
Unknown or incorrectly signed cards are rejected before PIN and key operations. The private key is generated and used inside the card.
MOONCOLD CARD COMPANION
Authenticate the card.
Verify its signing key.
The MoonCold Android app authenticates a supported Keycard 4.x card against the MoonCold Card CA, opens a protected NFC session, verifies the card PIN, creates or derives a card-held BIP-32 key, displays its Ethereum address and verifies a random local secp256k1 signing challenge.
Local companion tools
Check selected BTC, ETH, SOL and XRP public-address formats and test whether the phone detects an ISO-DEP card.
Offline by design
The app has no account, analytics SDK, advertising SDK or Internet permission. It does not fetch balances or broadcast transactions.
The current release performs card authentication, key derivation and a local signing check. It does not buy, sell, exchange, construct or broadcast cryptocurrency transactions.
App privacy policy