Back in Chapter 6, we went through how p2pk was inferior to p2pkh, in part because it was only protected by ECDSA. p2pkh, on the other hand, is also protected by sha256 and ripemd160. However, because the blockchain is public, once we spend from a ScriptPubKey corresponding to our address, we reveal our public key as part of the ScriptSig. Once we’ve revealed that public key, sha256 and ripemd160 no longer protect us, as the attacker knows the public key and doesn’t have to guess it.
As of this writing, we are still protected by the discrete log problem, which is unlikely to be broken any time soon. It’s important from a security perspective, however, to understand what we’re protected by.
The other reason to not reuse addresses is for privacy. Having a single address for all our transactions means that people can link our transactions together. If, for example, we bought something private (say, medication to treat some disease we don’t want others to know about) and spent another output with the same ScriptPubKey for a donation to some charity, the charity and the medication vendor could identify that we had done business with the other.
Privacy leaks tend to become security holes over time.
Back in Chapter 6, we went through how p2pk was inferior to p2pkh, in part because it was only protected by ECDSA. p2pkh, on the other hand, is also protected by sha256 and ripemd160. However, because the blockchain is public, once we spend from a ScriptPubKey corresponding to our address, we reveal our public key as part of the ScriptSig. Once we’ve revealed that public key, sha256 and ripemd160 no longer protect us, as the attacker knows the public key and doesn’t have to guess it.
As of this writing, we are still protected by the discrete log problem, which is unlikely to be broken any time soon. It’s important from a security perspective, however, to understand what we’re protected by.
The other reason to not reuse addresses is for privacy. Having a single address for all our transactions means that people can link our transactions together. If, for example, we bought something private (say, medication to treat some disease we don’t want others to know about) and spent another output with the same ScriptPubKey for a donation to some charity, the charity and the medication vendor could identify that we had done business with the other.
Privacy leaks tend to become security holes over time.