The fingerprint (normally along with the total derivation path for that key, which supplies the total key origin data) solely helps to establish the origin of a sure key. It doesn’t have an effect on the ensuing addresses, nonetheless:
- software program wallets use to establish which signing gadgets must be plugged so as to signal with a selected key; additionally they use it to accurately fill the assorted PSBT fields, which require the important thing origin data.
- signing gadgets can then use the knowledge within the PSBT so as to establish what keys within the descriptor are inside, and what are the derivation paths of the non-public keys they should derive and signal with.
With out the important thing origin data within the PSBT, signing gadgets would do not know what keys are their very own, what keys belong to cosigners, and what derivation paths to signal with.
Notice that storing that data as a part of your backup will not be elective: even for those who personal the seed (root key) from which a sure xpub is derived, there isn’t any assured manner to have the ability to deduce the derivation path for that xpub – which is important so as to have the ability to spend it. The one choice is brute-forcing all of the attainable paths, which basically will not be assured to achieve success, and even possible.
It’s in fact protected to strip the important thing origin data from the descriptor earlier than sending it to a 3rd social gathering that solely wants to make use of it so as to generate addresses, like a watch-only pockets.
