In this episode of “Bitcoin, Explained,” hosts Aaron van Wirdum and Sjors Provoost discuss reusing Bitcoin addresses. More specifically, they explain why reusing Bitcoin addresses is a bad idea.
Reusing Bitcoin addresses is a bad idea for roughly three reasons. The first two of these are that it harms privacy and impedes on Bitcoin’s censorship resistance . In the episode, van Wirdum and Provoost go over a couple examples of how such a loss of privacy and censorship resistance can negatively affect bitcoin users.
The third reason that reusing Bitcoin addresses is a bad idea is because it opens up the possibility of some niche attacks. In certain cases, attackers could extract private keys from signatures after coins are first spent from an address — though this does require that a wallet implemented the signing algorithm incorrectly in the first place. There are also some potential future scenarios where quantum computers could extract private keys from signatures if addresses are reused.
Another type of niche attack is a timing side-channel attack, such as the recently disclosed “Hertzbleed Attack.” Provoost explains that attackers can potentially derive a private key from a wallet by closely monitoring how the computer that hosts the wallet behaves when signing a transaction. This attack is more plausible if addresses are reused.
These aforementioned examples are some of the reasons why bitcoin users should refrain from using addresses more than once. Address reuse hurts users’ privacy and can potentially lead to a Hertzbleed Attack.