BIP-352 Silent Payments addresses should have an expiration time

Summary:

Josie expresses gratitude to Peter for his feedback regarding BIP352. Josie acknowledges that the issue of expiration dates is not specific to BIP352 but rather a general problem in Bitcoin. Josie suggests that if expiration dates are desired, they should be proposed and discussed as their own BIP. This would ensure that the expiration standard can work for various address formats such as xpubs, static payment codes, and existing/future formats. Josie raises skepticism about the effectiveness of expiration dates, stating that they weaken the value of silent payments and do not solve the problems described by Peter. Josie presents multiple scenarios to support this viewpoint:1. Compromised Wallet: If Bob's wallet is compromised with a one-year expiry, the attacker could update the expiration and continue receiving funds as Bob.2. Lost Keys: If Bob loses his keys with a one-year expiry but finds them three years later, the expiration causes him to miss out on two years of potential payments.3. Inheritance: If Bob dies with a one-year expiry and an heir inherits his backups years later, the expiration date prevents the heir from receiving payments for several years.4. Address Update Delay: If Bob is unable to update his address for several years but still has access to his keys/backups, the expiration date causes him to miss out on potential payments.5. Missed Payments: Even if Bob regularly updates his address with a new expiry, not all senders may find the updated address, resulting in missed payments.6. Metadata Leakage: By updating his address, Bob exposes metadata about himself, compromising his safety.Josie argues that instead of expiration dates, a better approach would be to allow Bob to revoke his silent payment address. Building a wallet protocol on top of silent payments could facilitate this. Furthermore, Josie highlights the privacy implications of expiration dates, as observers can determine that transactions mined at a certain block height are not payments to silent payment addresses with an expiry before that height.Regarding Peter's proposed solution, Josie notes that it is not enforceable as any wallet can ignore the extra bytes and send to the address/xpub/static payment code regardless. Josie suggests that for expiration dates to be useful, they would need to be enforced by consensus, but Josie is uncertain if this is a good idea.In conclusion, Josie states that expiration dates are a separate problem beyond the scope of BIP352. However, if a more general solution is found, it could potentially be added to a future version of silent payments. Nonetheless, Josie remains unconvinced that expiration dates for static payment codes are a good idea based on the aforementioned reasons.

Updated on: 2023-08-07T22:29:40.989369+00:00