Master key fingerprint requires unrestricted derivation path

[miketlk]

Description

For security reasons, the application would benefit from restricting the derivation paths available to it. While the current app database format allows specifying unrestricted access with "path": [null], a more secure configuration would specify explicit derivation paths, such as "path": ["44'/1'", "48'/1'", "49'/1'", "84'/1'", "86'/1'"]. However, the SDK currently lacks a function to return the master key fingerprint directly, forcing the app to derive the master pubkey instead.

Proposed Solution

Introduce a dedicated SDK function to return the 32-bit master key fingerprint without requiring the derivation of the master public key on the app's side. This would allow for more secure path restriction by eliminating the need for "path": [null] and to align the app database records with the current wallet apps' security requirements.

Remark

The corresponding Issue #821 was created in the ledger-secure-sdk to ask for this feature. If SDK maintainers consider that addition, this issue in the ledger-app-database could be closed as a duplicate.