HTLC_FLOW.md

HTLC Flow Implemented with only one offer at a time.

We Offer an HTLC

Create HTLC

• make new HTLC
• increment htlc-next-offer-id
• offer.htlc-state
  • add new HTLC
  • store her-commit TXID
  • store her-commit revocation-pubkey
• sign and add new HTLC to her-commit
• sign her-commit
• send commitment-signed
  • new HTLC
  • all HTLC sigs w/ id
  • her-commit witness

Receive revoke_and_ack

Use offer.htlc-state

• ?> per-commitment-secret produces revocation-pubkey
• generate revoke-privkey
• add prior-txid& revoke-privkey to revocations
• move next-per-commitment-point to per-commitment-point
• update next-per-commitment-point to one in this msg don't delete offer.htlc-state

Receive commitment_signed

• ?> num-htlcs is num in our-commit + 1
• ?> one of the HTLC signatures matches our offer.htlc-state
• compute our next-per-commitment-point
• send revoke_and_ack for our-commit with next-per-commitment-point
• add offer.htlc-state to our-commit
• delete offer.htlc-state

---

We Receive an HTLC

Receive update_add_htlc & commitment_signed

• ?> HTLC id is htlc-next-receive-id
• increment htlc-next-receive-id
• add HTLC to our-commit
• receive.htlc-state
  • add HTLC
  • store our-commit TXID
  • store our-commit revocation-pubkey
• compute our next-per-commitment-point
• send revoke_and_ack for our-commit with next-per-commitment-point

Receive revoke_and_ack

• Use offer.htlc-state
• ?> per-commitment-secret produces revocation-pubkey
• generate revoke-privkey
• add prior-txid& revoke-privkey to revocations
• move next-per-commitment-point to per-commitment-point
• update next-per-commitment-point to one in this msg
• delete receive.htlc-state

Now can go ahead and pay HTLC or offer to next hop, if applicable.