If we make an Android dapp, can't we use Android intents to sign a transaction in another Android wallet app that supports receiving data through intents? We can pass message and public key in the intent (e.g. using subxt) , and wallet makes transaction. Will there be any security issues? Though we can't connect the wallet to get the public key, we can just copy the public key from the wallet and paste it on the dapp, to get the dapp UI for the public key.
Another approach could involve creating a trusted server apps responsible for handling transactions and securely storing private keys or seeds. Authentication mechanisms can be implemented to ensure that only trusted applications on the computer can access the server API. This approach effectively separates the authentication logic from the dapp itself, similar to browser extensions wallet, and can also be utilized on desktop systems where "intents" are not available.
Here, two passwords can be utilized: one for communication between the Dapp and the server, which the Dapp can interact with, and another password for signing transactions, similar to how MetaMask or the Polkadot.js extension wallet operates, where only the server application can interact with this password.