Lightning Network Watchtower blockchain.tokyo #8 @parakeety 

ࣗݾ঺հ • Ԭా༸ฏ • github: parakeety • twitter: @parakeety_ • ڵຯؔ৺: Lightning Network, DEX, mimblewimble 

Lightning Network͓͞Β͍ • Bitcoin networkͱ࿈ܞ͢Δ΋͏Ұͭͷp2p network • opening txͱclosing tx͸Bitcoin networkʹbroadcast͞ Εॻ͖ࠐ·ΕΔ͕ɺ్தͷcommitment tx͸broadcast ͤͣʹͻͨ͢Βߋ৽͢Δ • commitment tx͸ॺ໊ࡁΈͰ͍ͭͰ΋Bitcoin network ʹ͍ͭͰ΋broadcastͯ֬͠ఆͤ͞Δࣄ͕Ͱ͖Δ 

0QFOJOH
5SBOTBDUJPO $MPTJOH
5SBOTBDUJPO $PNNJUNFOU
5SBOTBDUJPO  $PNNJUNFOU
5SBOTBDUJPO  ΞυϨεA: 5BTC ΞυϨεB: 5BTC ΞυϨεA: 4BTC ΞυϨεB: 6BTC ΞυϨεA͔ΒΞυϨεBʹ1BTCૹۚ ΞυϨεAͷॴ༗ऀ͸Commitment Transaction(1)Λbroadcast͢Δincentive͕͋Δ 

ݹ͍ෆਖ਼ͳCommitment TxΛbroadcastͨ͠৔߹ • ҰఆظؒҎ಺ʹɺऔΓ໭͢tx(justice tx)Λ࡞੒ͯ͠ broadcast͢Ε͹ɺopening txͷdepositΛશͯճऩ͢ Δࣄ͕Ͱ͖Δ 

ෆਖ਼ͳCommitment txճऩͷ՝୊ • ݹ͍ෆਖ਼ͳcommitment tx͕broadcast͞Ε͔ͯΒɺҰ ఆظؒҎ಺ʹjustice txΛ࡞੒ͯ͠ɺbroadcast͠ͳ͍ͱ ͍͚ͳ͍ • ͭ·ΓɺBitcoin networkΛ؂ࢹ͢Δඞཁ͕͋Δ • ৗ࣌ىಈ͍ͯ͠Δfull nodeͰ͋Ε͹Մೳ͕ͩɺϞόΠϧ ୺຤ͩͱݫ͍͠ 

Watchtower 

Watchtower • ϞόΠϧ୺຤ͳͲͷৗ࣌ىಈ͕೉͍ܰ͠ྔΫϥΠΞϯτ ͷ୅ΘΓʹɺBitcoin NetworkΛ؂ࢹ • ݹ͍Commitment tx͕broadcast͞ΕͨͷΛݕ஌͠ɺ justice txΛbroadcastͯ͘͠ΕΔ • LightningͷϑϧϊʔυͷҰػೳͱ࣮ͯ͠૷༧ఆ 

Watchtowerͷ࢓૊Έ • ܰྔΫϥΠΞϯτ͸ɺCommitment txΛߋ৽͢Δ౓ ʹɺjustice txΛ࡞੒͠ɺWatchtowerʹૹΔ • ͋ͱ͸Watchtower͕ࣗಈͰճऩͯ͘͠ΕΔ • 1ͭͷWatchtowerͰ͸ͳͯ͘ɺෳ਺ͷWatchtowerʹ outsource͢Δ 

WatchtowerͷΠϯηϯςΟϒ • ܰྔΫϥΠΞϯτͷ୅ΘΓʹෆਖ਼ͳCommitment txΛ ৗ࣌؂ࢹͯ͠΋Β͏ࣄʹରͯ͠ରՁΛ෷͏ࣄ͕૝ఆ͞Ε ͯΔ • Retribution: ճऩֹͨۚ͠ͷҰ෦ΛWatchtowerʹࢧ෷ ͏ • Pay-per-state: Commitment txΛߋ৽͠ɺjustice txΛૹ Δ౓ʹใुΛࢧ෷͏ 

·ͱΊ • ϞόΠϧ୺຤ͷৗ࣌ىಈ͕೉͍͠ΫϥΠΞϯτͰ΋҆৺ ͯ͠Lightning NetworkΛ࢖͑ΔΑ͏ʹͳΔʹ͸ɺ Watchtower͕ඞཁ