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Add min_final_expiry_delta to blinded route example (#1131)

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Payment recipients must ensure that they have a few blocks
before fulfilling the payment, in case the inbound channel
force-closes.
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Bastien Teinturier 2024-01-30 06:52:29 +01:00 • committed by GitHub
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proposals/route-blinding.md
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@ -253,11 +253,12 @@ receive slightly less than intended):
* `route_fee_base_msat(n+1) = (fee_base_msat(n+1) * 1000000 + route_fee_base_msat(n) * (1000000 + fee_proportional_millionths(n+1)) + 1000000 - 1) / 1000000` * `route_fee_base_msat(n+1) = (fee_base_msat(n+1) * 1000000 + route_fee_base_msat(n) * (1000000 + fee_proportional_millionths(n+1)) + 1000000 - 1) / 1000000`
* `route_fee_proportional_millionths(n+1) = ((route_fee_proportional_millionths(n) + fee_proportional_millionths(n+1)) * 1000000 + route_fee_proportional_millionths(n) * fee_proportional_millionths(n+1) + 1000000 - 1) / 1000000` * `route_fee_proportional_millionths(n+1) = ((route_fee_proportional_millionths(n) + fee_proportional_millionths(n+1)) * 1000000 + route_fee_proportional_millionths(n) * fee_proportional_millionths(n+1) + 1000000 - 1) / 1000000`
This yields the following values: Alice wants to use a `min_final_cltv_expiry_delta` of 12 blocks, which she adds to the route's
total `cltv_expiry_delta`. This yields the following values:
* `route_fee_base_msat`: 201 * `route_fee_base_msat`: 201
* `route_fee_proportional_millionths`: 1001 * `route_fee_proportional_millionths`: 1001
* `route_cltv_expiry_delta`: 288 * `route_cltv_expiry_delta`: 300
Let's assume the current block height is 1000. Alice wants the route to be used in the next 200 Let's assume the current block height is 1000. Alice wants the route to be used in the next 200
blocks, so she sets `max_cltv_expiry = 1200` and adds `cltv_expiry_delta` for each hop. Alice then blocks, so she sets `max_cltv_expiry = 1200` and adds `cltv_expiry_delta` for each hop. Alice then
@ -269,7 +270,7 @@ transmits the following information to the sender (most likely via an invoice):
* `fee_base_msat`: 201 * `fee_base_msat`: 201
* `fee_proportional_millionths`: 1001 * `fee_proportional_millionths`: 1001
* `htlc_minimum_msat`: 1000 * `htlc_minimum_msat`: 1000
* `cltv_expiry_delta`: 288 * `cltv_expiry_delta`: 300
* `max_cltv_expiry`: 1200 (may be conveyed via invoice expiration, assuming 10 minute blocks) * `max_cltv_expiry`: 1200 (may be conveyed via invoice expiration, assuming 10 minute blocks)
* `allowed_features`: empty * `allowed_features`: empty
* Encrypted data for blinded nodes: * Encrypted data for blinded nodes:
@ -281,13 +282,13 @@ transmits the following information to the sender (most likely via an invoice):
* `fee_base_msat`: 100 * `fee_base_msat`: 100
* `fee_proportional_millionths`: 500 * `fee_proportional_millionths`: 500
* `htlc_minimum_msat`: 1000 * `htlc_minimum_msat`: 1000
* `max_cltv_expiry`: 1344 * `max_cltv_expiry`: 1356
* `encrypted_payload(carol)`: * `encrypted_payload(carol)`:
* `outgoing_channel_id`: `scid_carol_bob` * `outgoing_channel_id`: `scid_carol_bob`
* `fee_base_msat`: 100 * `fee_base_msat`: 100
* `fee_proportional_millionths`: 500 * `fee_proportional_millionths`: 500
* `htlc_minimum_msat`: 1000 * `htlc_minimum_msat`: 1000
* `max_cltv_expiry`: 1488 * `max_cltv_expiry`: 1500
Note that the introduction point (Carol) uses the real `node_id`, not the blinded one, because the Note that the introduction point (Carol) uses the real `node_id`, not the blinded one, because the
sender needs to be able to locate this introduction point and find a route to it. The sender will sender needs to be able to locate this introduction point and find a route to it. The sender will
@ -314,7 +315,7 @@ chosen by adding a random cltv offset to the current block height as described i
Erin computes the expiry that should be sent to Carol: Erin computes the expiry that should be sent to Carol:
* `expiry = 1100 + 288 = 1388` * `expiry = 1100 + 300 = 1400`
When a node in the blinded route receives an htlc, the onion will not contain the `amt_to_forward` When a node in the blinded route receives an htlc, the onion will not contain the `amt_to_forward`
or `outgoing_cltv_value`. They will have to compute them based on the fields contained in their or `outgoing_cltv_value`. They will have to compute them based on the fields contained in their
@ -323,12 +324,12 @@ or `outgoing_cltv_value`. They will have to compute them based on the fields con
For example, here is how Carol will compute the values for the htlc she relays to Bob: For example, here is how Carol will compute the values for the htlc she relays to Bob:
* `amount = ((100302 - fee_base_msat) * 1000000 + 1000000 + fee_proportional_millionths - 1) / (1000000 + fee_proportional_millionths) = 100152 msat` * `amount = ((100302 - fee_base_msat) * 1000000 + 1000000 + fee_proportional_millionths - 1) / (1000000 + fee_proportional_millionths) = 100152 msat`
* `expiry = 1388 - cltv_expiry_delta = 1244` * `expiry = 1400 - cltv_expiry_delta = 1256`
And here is how Bob computes the values for the htlc he relays to Alice: And here is how Bob computes the values for the htlc he relays to Alice:
* `amount = ((100152 - fee_base_msat) * 1000000 + 1000000 + fee_proportional_millionths - 1) / (1000000 + fee_proportional_millionths) = 100002 msat` * `amount = ((100152 - fee_base_msat) * 1000000 + 1000000 + fee_proportional_millionths - 1) / (1000000 + fee_proportional_millionths) = 100002 msat`
* `expiry = 1244 - cltv_expiry_delta = 1100` * `expiry = 1256 - cltv_expiry_delta = 1112`
Note that as the rounding errors aggregate, the recipient will receive slightly more than what was Note that as the rounding errors aggregate, the recipient will receive slightly more than what was
expected. The sender includes `amt_to_forward` in the onion payload for the recipient to let them expected. The sender includes `amt_to_forward` in the onion payload for the recipient to let them
@ -342,24 +343,24 @@ The messages exchanged will contain the following values:
| update_add_htlc | update_add_htlc | update_add_htlc | update_add_htlc | | update_add_htlc | update_add_htlc | update_add_htlc | update_add_htlc |
| +--------------------------------+ | +------------------------------------------+ | +------------------------------------------+ | +--------------------------------+ | | +--------------------------------+ | +------------------------------------------+ | +------------------------------------------+ | +--------------------------------+ |
| | amount: 100322 msat | | | amount: 100302 msat | | | amount: 100152 msat | | | amount: 100002 msat | | | | amount: 100322 msat | | | amount: 100302 msat | | | amount: 100152 msat | | | amount: 100002 msat | |
| | expiry: 1412 | | | expiry: 1388 | | | expiry: 1244 | | | expiry: 1100 | | | | expiry: 1424 | | | expiry: 1400 | | | expiry: 1256 | | | expiry: 1112 | |
| | onion_routing_packet: | | | onion_routing_packet: | | | onion_routing_packet: | | | onion_routing_packet: | | | | onion_routing_packet: | | | onion_routing_packet: | | | onion_routing_packet: | | | onion_routing_packet: | |
| | +----------------------------+ | | | +--------------------------------------+ | | | +--------------------------------------+ | | | +----------------------------+ | | | | +----------------------------+ | | | +--------------------------------------+ | | | +--------------------------------------+ | | | +----------------------------+ | |
| --> | | amount_fwd: 100302 msat | | --> | --> | | blinding_eph_key: E(carol) | | --> | --> | | encrypted_data: | | --> | --> | | amount_fwd: 100000 msat | | --> | | --> | | amount_fwd: 100302 msat | | --> | --> | | blinding_eph_key: E(carol) | | --> | --> | | encrypted_data: | | --> | --> | | amount_fwd: 100000 msat | | --> |
| | | outgoing_expiry: 1388 | | | | | encrypted_data: | | | | | +----------------------------------+ | | | | | outgoing_expiry: 1100 | | | | | | outgoing_expiry: 1400 | | | | | encrypted_data: | | | | | +----------------------------------+ | | | | | outgoing_expiry: 1112 | | |
| | | scid: scid_dave_to_carol | | | | | +----------------------------------+ | | | | | | scid: scid_bob_to_alice | | | | | | encrypted_data: | | | | | | scid: scid_dave_to_carol | | | | | +----------------------------------+ | | | | | | scid: scid_bob_to_alice | | | | | | encrypted_data: | | |
| | +----------------------------+ | | | | | scid: scid_carol_to_bob | | | | | | | fee_base_msat: 100 | | | | | | +-----------------------+ | | | | | +----------------------------+ | | | | | scid: scid_carol_to_bob | | | | | | | fee_base_msat: 100 | | | | | | +-----------------------+ | | |
| | | blinding_eph_key: E(carol) | | | | | | fee_base_msat: 100 | | | | | | | fee_proportional_millionths: 500 | | | | | | | path_id: preimage | | | | | | | blinding_eph_key: E(carol) | | | | | | fee_base_msat: 100 | | | | | | | fee_proportional_millionths: 500 | | | | | | | path_id: preimage | | | |
| | | encrypted_data(carol) | | | | | | fee_proportional_millionths: 500 | | | | | | | htlc_minimum_msat: 1000 | | | | | | | max_cltv_expiry: 1200 | | | | | | | encrypted_data(carol) | | | | | | fee_proportional_millionths: 500 | | | | | | | htlc_minimum_msat: 1000 | | | | | | | max_cltv_expiry: 1200 | | | |
| | +----------------------------+ | | | | | htlc_minimum_msat: 1000 | | | | | | | cltv_expiry_delta: 144 | | | | | | +-----------------------+ | | | | | +----------------------------+ | | | | | htlc_minimum_msat: 1000 | | | | | | | cltv_expiry_delta: 144 | | | | | | +-----------------------+ | | |
| | | encrypted_data(bob) | | | | | | cltv_expiry_delta: 144 | | | | | | | max_cltv_expiry: 1344 | | | | | +----------------------------+ | | | | | encrypted_data(bob) | | | | | | cltv_expiry_delta: 144 | | | | | | | max_cltv_expiry: 1356 | | | | | +----------------------------+ | |
| | +----------------------------+ | | | | | max_cltv_expiry: 1488 | | | | | | +----------------------------------+ | | | | tlv_extension | | | | +----------------------------+ | | | | | max_cltv_expiry: 1500 | | | | | | +----------------------------------+ | | | | tlv_extension | |
| | | amount_fwd: 100000 msat | | | | | +----------------------------------+ | | | | +--------------------------------------+ | | | +----------------------------+ | | | | | amount_fwd: 100000 msat | | | | | +----------------------------------+ | | | | +--------------------------------------+ | | | +----------------------------+ | |
| | | outgoing_expiry: 1100 | | | | +--------------------------------------+ | | | | amount_fwd: 100000 msat | | | | | blinding_eph_key: E(alice) | | | | | | outgoing_expiry: 1112 | | | | +--------------------------------------+ | | | | amount_fwd: 100000 msat | | | | | blinding_eph_key: E(alice) | | |
| | | encrypted_data(alice) | | | | | encrypted_data(bob) | | | | | outgoing_expiry: 1100 | | | | +----------------------------+ | | | | | encrypted_data(alice) | | | | | encrypted_data(bob) | | | | | outgoing_expiry: 1112 | | | | +----------------------------+ | |
| | +----------------------------+ | | | +--------------------------------------+ | | | | encrypted_data(alice) | | | +--------------------------------+ | | | +----------------------------+ | | | +--------------------------------------+ | | | | encrypted_data(alice) | | | +--------------------------------+ |
| +--------------------------------+ | | | amount_fwd: 100000 msat | | | | +--------------------------------------+ | | | | +--------------------------------+ | | | amount_fwd: 100000 msat | | | | +--------------------------------------+ | | |
| | | | outgoing_expiry: 1100 | | | | tlv_extension | | | | | | | outgoing_expiry: 1112 | | | | tlv_extension | | |
| | | | encrypted_data(alice) | | | | +--------------------------------------+ | | | | | | | encrypted_data(alice) | | | | +--------------------------------------+ | | |
| | | +--------------------------------------+ | | | | blinding_eph_key: E(bob) | | | | | | | +--------------------------------------+ | | | | blinding_eph_key: E(bob) | | | |
| | +------------------------------------------+ | | +--------------------------------------+ | | | | | +------------------------------------------+ | | +--------------------------------------+ | | |