I had written a blog post about the concept and it was shared on mailing list in July 2024. There wasn’t any response on mailing list but I have discussed it with some developers and there seems to be lot of interest for the idea among users.
This is an initial draft and the pull request will help me complete the BIP ASAP.
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1+ BIP: XXX
2+ Layer: Applications
3+ Title: Octojoin v1
4+ Author: /dev/fd0 <alicexbt@protonmail.com>
5+ Type: Informational
Please add the following 2 lines before this line (see BIP-2):
0Comments-URI: https://github.com/bitcoin/bips/wiki/Comments:BIP-0xxx
1Status: Draft
18+
19+====Relation to Monero====
20+
21+Most Monero transactions use 16 ring size for the input, making it impossible to determine which input is signed by the user out of 16. The amounts are hidden, and stealth addresses are used for outputs.
22+
23+Octojoin achieves partial obfuscation similar to Monero's ring signatures ([https://www.getmonero.org/2024/04/27/fcmps.html FCMP++] will replace ring signatures in future) and stealth addresses. Swaps can be done off-chain to obscure the transaction's input ownership and history.
0Octojoin achieves partial obfuscation similar to Monero's ring signatures ([https://www.getmonero.org/2024/04/27/fcmps.html FCMP++] will replace ring signatures in the future) and stealth addresses. Swaps can be done off-chain to obscure the transaction's input ownership and history.
72+
73+Proof of Concept: TBD
74+
75+==Backwards Compatibility==
76+
77+This is a new protocol and has no compatibility issues. It is not a replacement for payjoin either and benefits from multiple interpretations on-chain.
8+
9+==Introduction==
10+
11+===Abstract===
12+
13+This document describes the process to use swapped UTXOs for inputs, silent payment addresses for outputs, and hide the transacted amount with multiple interpretations.
0This document describes the process to use swapped UTXOs for inputs, [[bip-0352.mediawiki|BIP 352]] silent payment addresses for outputs, and hide the transacted amount with multiple interpretations.
12+
13+This document describes the process to use swapped UTXOs for inputs, silent payment addresses for outputs, and hide the transacted amount with multiple interpretations.
14+
15+===Motivation===
16+
17+Payjoin requires coordination and sharing of UTXOs between sender and recipient. This affects privacy and UX in some cases. Octojoin avoids sharing of UTXOs and uses swapped UTXOs.
83+ x-axis [Jan, Feb, Mar, Apr, May, Jun, Jul, Aug, Sep]
84+ y-axis "Transactions (in thousands)" 0 --> 160
85+ bar [125, 143, 157, 130, 117, 106, 121, 123, 127]
86+</source>
87+
88+Transactions that already use 3 inputs and 2 outputs will serve as the anonymity set for octojoin transactions with default values. It is possible to change defaults and use more number of inputs and outputs.
0Transactions that already use 3 inputs and 2 outputs will serve as the anonymity set for octojoin transactions with default values. It is possible to change defaults and use a higher number of inputs and outputs.
87+
88+Transactions that already use 3 inputs and 2 outputs will serve as the anonymity set for octojoin transactions with default values. It is possible to change defaults and use more number of inputs and outputs.
89+
90+====Swapped UTXOs====
91+
92+Swapping UTXOs off-chain will obscure the transaction's input ownership and history. It also adds more noise on-chain to make chain analysis difficult
0Swapping UTXOs off-chain will obscure the transaction's input ownership and history. It also adds more noise on-chain to make chain analysis difficult.
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