So, you have a Ledger (or Trezor) seed, and you want to use it with a Trezor (or vice-versa, a Ledger). Will your old seed work in the other device, in order to recover your Monero keys?
Unfortunately, Ledger and Trezor ended up using different key derivation algorithms. Such that using the same 24 word seed results in different keys between the devices.
To quote a Trezor developer on Github:
In our upcoming Monero implementation for Trezor, we plan to use SLIP-0010 as our primary derivation method.
If I’m not mistaken the current Ledger implementation uses BIP-32 scheme with secp256k1 and then converts the secp256k1 point into a ed25519 point. SLIP-0010 takes a different apporach and specifies how to derive a BIP-32-like path on ed25519 curve directly.
Does Monero have any opinion on this? We believe the Monero community should agree on some “standard” to allow compatibility between different HW vendors. Failing to do so would lead to an inconsistency where the same mnemonic seed does not converge to the same wallet.
So it appears that Ledger picked one derivation method, and then later, Trezor picked another.
That’s unfortunate – but there we go!
To quote one user in the thread: