Multiple private keys on ledger devices

Question

I have read Ledger devices can handle multiple "applications". I suppose an application means a cryptocurrency (btc, eth, etc.).

Is there a private key for each application or is it a single private key for all applications ?

Thanks

Answer 1

I suppose an application means a cryptocurrency (btc, eth, etc.).

This is usually, but not always, the case - for instance, the Ethereum application on the ledger device handles Ethereum, Ethereum Classic, and many other chains that are ethereum forks.

Is there a private key for each application or is it a single private key for all applications ?

Ledgers use BIP 32/39/44 to derive keys from a single root key, expose that root key as seed words for ease of backup, and follow a common convention for deciding which coin will derive which subkeys from the root.

Each ledger application accepts a derivation path as part of its usage. This path specified how to derive the subkey(s) required from the root key. The device will then derive them and sign the transaction, without exposing the keys to the controlling computer.