Original Paper: Homomorphic Payment Addresses and the Pay-to-Contract Protocol

Pay-to-Contract transaction with signaling output tx.

Client

get merchant's pubkey and order-format(JSON format)
build transaction for buying order and send bitcoin
upload json to IPFS

Server

watch blockchain to search signaling tx.
get IPFS location from signal
lookup order contract from ipfs

development tips

use insight api on regtest mode: https://www.oodlestechnologies.com/blogs/Create-Bitcoin-Explorer-Using-Bitcoind-And-Bitcore-Insight
btcregtestinsight: https://github.com/starcharles/btcregtest-insight

TODO

make as a library
publish as npm package
option to use blockCypher API/ bitcore light client
remove OP_RETURN with IPFS tag