In a forward-thinking post to the Bitcoin-Dev mailing list, renowned Bitcoin Core developer and founder of OpenTimestamps, Peter Todd, has advanced the Bitcoin Improvement Proposal 352 (BIP-352) for integrating user-defined expiration dates to silent payment addresses in a bid to address concerns related to compromised or lost wallets.

Todd’s idea stems from a fundamental issue surrounding wallets that eventually fall into disuse. He postulates, “Wallets don’t last forever. They are often compromised or lost. When this happens, the addresses generated from those wallets become a form of toxic data: funds sent to those addresses can be easily lost forever.”

#Bitcoin Update: @peterktodd suggests adding user-set expiration dates to $BTC addresses for silent payments. pic.twitter.com/zIqaSvyRmK

— Jake Simmons (@realJakeSimmons) August 16, 2023

A Proposal For More Bitcoin Privacy

Silent payments, a progressive development in the realm of BTC privacy, are particularly vulnerable. Unlike traditional Bitcoin addresses which are intended for one-time use, silent payments are designed for repeated transactions to the same address without compromising privacy.

As described on GitHub, silent payments enable users to “receive private payments from anyone on a single static address without requiring any interaction or extra on-chain overhead.”

Given their recurrent nature, Todd argues, “Failing to make Silent Payment addresses eventually expire in a reasonable amount of time is thus a particularly harmful mistake.”

To rectify this potential flaw, Todd’s proposal suggests integrating an expiration mechanism into silent payment addresses. His recommendation details an addition of “a 3 byte field to silent payments addresses, encoding the expiration date in terms of days after some epoch. 2^24 days is 45,000 years, more than enough. Indeed, 2 bytes is probably fine too: 2^16 days is 180 years.” He adds a touch of wry humor, jesting, “We’ll be lucky if Bitcoin still exists in 180 years.”

A key facet of this proposal is the user experience. Silent payments, with their potential for enhancing privacy, should also be convenient and secure for users. As Todd opines, “Wallets should pick a reasonable default, e.g. 1 year, for newly created addresses. Attempts to pay an expired address should just fail with a simple address expired.”

It’s evident that Todd’s proposal addresses concerns that are quintessential for the evolving of Bitcoin. While Bitcoin Optech Newsletter #264 noted that the recommendation “received a moderate amount of discussion on the mailing list, with no clear resolution as of this writing”, the importance of this discourse cannot be understated for those invested in the future of Bitcoin and its underlying technology.

The ramifications of this proposal, if accepted and integrated, could shape the next phase of BTC’s journey, particularly as it pertains to user privacy and security.

At press time, the BTC price stood at $29,153.