user120768: I was looking into wallets and the information that they contain. I found this post:
What information does a wallet contain?
I thought that wallets have only one key pair. Why is there more than one key pair in a wallet?

user5406: Most wallets have indeed only one main secret, but they use it to generate many different addresses.
When you receive a payment in Bitcoin, the sender locks up funds with a locking script that can only be spent using your private key. The locking scripts are deterministically derived from your public key and visible to all other users on the network. If you were to use only a single key pair, any observer on the network could assume that all the corresponding funds belong to the same user and could easily cluster all your payments.
Wallets generally steer the user towards using a new address for every payment they receive, to decouple funds and achieve some financial privacy. However, if all of those keys were unrelated, we'd have to make a new wallet backup after every payment, so today's wallets generally work by having one main secret from which any number of sub-keys are derived for the individual payments.

120768: <p>I was looking into wallets and the information that they contain. I found this post:</p>
<p><a href="https://bitcoin.stackexchange.com/q/3173/120768">What information does a wallet contain?</a></p>
<p>I thought that wallets have only one key pair. Why is there more than one key pair in a wallet?</p>
 5406: <p>Most wallets have indeed only one main secret, but they use it to generate many different addresses.</p>
<p>When you receive a payment in Bitcoin, the sender locks up funds with a locking script that can only be spent using your private key. The locking scripts are deterministically derived from your public key and visible to all other users on the network. If you were to use only a single key pair, any observer on the network could assume that all the corresponding funds belong to the same user and could easily <a href="https://en.bitcoin.it/wiki/Privacy#Address_reuse" rel="nofollow noreferrer">cluster all your payments</a>.</p>
<p>Wallets generally steer the user towards using a new address for every payment they receive, to decouple funds and achieve some financial privacy. However, if all of those keys were unrelated, we'd have to make a new wallet backup after every payment, so today's wallets generally work by having one main secret from which any number of sub-keys are <a href="https://github.com/bitcoin/bips/blob/master/bip-0032.mediawiki" rel="nofollow noreferrer">derived</a> for the individual payments.</p>
