Polkadot Vault is a mobile application solution for secure, air-gapped cold storage of cryptocurrency keys, turning any smartphone into a disconnected crypto wallet. Designed for both iOS and Android platforms, it enables the creation and management of accounts on Substrate-based networks, facilitating message signing and transactions without any active connectivity, thereby minimizing exposure to online threats. The application employs QR codes for all data transfers, ensuring private keys remain secure on the device, and supports networks such as Polkadot and Kusama. Built on a robust Rust core with native Swift and Kotlin interfaces, Polkadot Vault provides features including multiple key generation, transaction parsing and signing, account backup, and multi-address support, all within a framework designed for maximum offline security.