research-lab

In Monero, this is known as a "subaddress", and has recently undergone review by the Monero cryptographers. https://github.com/b-g-goodell/research-lab/blob/master/publ... All I can really say is that the cryptonote protocol was probably designed to focus on privacy within the blockchain. Intrablockchain privacy. Anything out-of band was not considered within scope, maybe. I'm just speculating because who knows what the cryptonote developers were thinking. The Monero core team is working to advance what cryptonote started, and subaddresses are a step in the right direction.

edit: I just found a paper [1] which talks about this issue and a potential solution. Monero certainly has lots of things that make me excited about it, but it seems there is a downside: To recieve a payment, 'A' must tell the sender ('B') A's recieve address. Now, this recieve address is never encoded in the block chain, but it is known to everyone who sends 'A' coins. If 'B' and others who know 'A's recieve address keep track of it and the coins they send, some privacy is not preserved. Bitcoin & many other crypto curencies "solve" this to some extent by using Hierarchical Deterministic wallets ("HD wallets") were a single secret plus a deterministic "count" is used to generate multiple "accounts", each with it's own receive address. The problem is that it isn't clear to me Monero has any HD wallet implementations, and I'm not familiar