notmandatory

# install bitcoind via your favorite method

# start regtest bitcoind
mkdir -p /tmp/regtest1/bitcoind
bitcoind -datadir=/tmp/regtest1/bitcoind -regtest -server -fallbackfee=0.0002 -rpcallowip=0.0.0.0/0 -rpcbind=0.0.0.0 -blockfilterindex=1 -peerblockfilters=1 -daemon

# cookie file location: /tmp/regtest1/bitcoind/regtest/.cookie

# create test bitcoind wallet
bitcoin-cli -datadir=/tmp/regtest1/bitcoind -regtest -named createwallet wallet_name="regtest1" disable_private_keys=true blank=true

notmandatory

Privacy preserving multi-sig signing service

Problem

Create a signing service that when properly authorized will add valid signatures to a client's PSBT without knowing the client's full wallet history. The signing service must be able to determine the transaction spending amount. The client must be able to sign and finalize a transactions independently of the service.

Solution

1. For each client the signing service creates a signing bip39 xprv key and shares the corresponding xpub with the client's software. The signing service does not need to share any root key information with the client except the key fingerprint. Example:

notmandatory

Some notes on my manual rpc cli setup and testing:

1. start bitcoind in regtest mode

mkdir /tmp/bitcoind
bitcoind -datadir=/tmp/bitcoind -regtest -server -fallbackfee=0.0002 -rpcallowip=0.0.0.0/0 -rpcbind=0.0.0.0 -blockfilterindex=1 --peerblockfilters=1 -daemon

2. create bitcoind test wallet and generate blocks

bitcoin-cli -datadir=/tmp/bitcoind -regtest createwallet "test"

notmandatory

echo create temp diretory to store bitcoind data
mkdir -p /tmp/regtest1/bitcoind

echo start bitcoind in regtest mode
bitcoind -datadir=/tmp/regtest1/bitcoind -regtest -server -fallbackfee=0.0002 -rpcallowip=0.0.0.0/0 -rpcbind=0.0.0.0 -blockfilterindex=1 -peerblockfilters=1 -daemon

echo create blank descriptor wallet
bitcoin-cli -datadir=/tmp/regtest1/bitcoind -regtest -named createwallet wallet_name="regtest1" blank=true disable_private_keys=true
{