DLC sample for ECDSA

dlc.rb

# using bitcoinrb
require 'bitcoin'

# oracle

# oracle's key. V = vG
o_key = Bitcoin::Key.new(priv_key: '860f6a0296aae3901e374be83d962351366386fb5f65ffef75c9f389c256e724')
V = o_key.to_point
v = o_key.priv_key.to_i(16)

# onetime signature nonce. R = kG
tmp_key = Bitcoin::Key.new(priv_key: '8f9e7a509b0c33aecff16c0707c2ffc5ba051ca70b4d031de98a13f88cb51380')
R = tmp_key.to_point
k = tmp_key.priv_key.to_i(16)

# Alice generate s100 pubkey.
alice_key = Bitcoin::Key.new(priv_key: 'eabeba881f9a975b16b96e40df3c9412d052a85a655255629dc9906e4a6de6ac')

R_str = ECDSA::Format::PointOctetString.encode(R, compression: true)
R_hash_value = Bitcoin.sha256((100.to_s(16) + R_str).htb).to_i(16)

# create many pubkey for i. following i == 100.
s100_G = R + V.multiply_by_scalar(R_hash_value).negate # s100G = R - h(100, R)V
alice_100_pubkey = alice_key.to_point + s100_G # Alice's pubkey + s100G
puts "alice_100_pubkey = #{ECDSA::Format::PointOctetString.encode(alice_100_pubkey, compression: true).bth}"

# Bob create contract like Alice's
#...

# oracle create signature.
hash_value = R_hash_value * v % ECDSA::Group::Secp256k1.order # h(100, R)v
s100 = (k - hash_value) % ECDSA::Group::Secp256k1.order # s100 = k - h(100, R)v

# oracle publish s100

# alice create unlock key using s100 and her private key.
alice_unlock_key = Bitcoin::Key.new(priv_key: ((alice_key.priv_key.to_i(16) + s100) % ECDSA::Group::Secp256k1.order).to_s(16))

# alice_100_pubkey == alice_unlock_key's pub
puts "alice_unlock_key = #{alice_unlock_key.pubkey}"
puts ECDSA::Format::PointOctetString.encode(alice_100_pubkey, compression: true).bth == alice_unlock_key.pubkey