Questions tagged [hash-time-locked-contract]

A Hash Time Locked Contract (HTLC) is a conditional payment that requires the recipient to reveal a hash preimage. It also includes a time lock clause that allows the payment to be refunded after a certain time. HTLCs are used in Lightning Network channels, atomic swaps and other protocols.

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3 answers
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"HTLCs don't work for micropayments"?

I read this tweet by Tadge Dryja recently. What exactly did he mean? Is this an issue? If so, is this issue fixable?
10 votes
1 answer
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How is a node in the middle prohibited from keeping the money in a routed Payment in Lightning network?

It is my understanding that Lightning is to scale with users having only few payment channels by leveraging the six degrees of separation theory to facilitate payment routing. I understand how onion ...
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9 votes
1 answer
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Can PTLCs and HTLCs be mixed along a route?

When PTLCs get introduced on the Lightning Network, do all hops along a route need to use just one of either HTLCs or PTLCs, or would it be possible to create a route where some nodes use PTLCs and ...
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8 votes
1 answer
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What is a hash pre-image as it is used for the breach remedy?

Until this afternoon I thought the anti-cheat transactions or breach remedies built on the exit-transaction of the counterparty. Apparently, they build on something called a "hash pre-image". What is ...
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7 votes
2 answers
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What does the abbreviation "HTLC" stand for?

An HTLC is a contract making use of both a hashlock and a timelock. I noticed a discrepancy in what various sources state the abbreviation HTLC is short for. I've found: "Hashed Timelock ...
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5 votes
2 answers
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HTLC (Hash Time Lock Contract) using bitcoin-qt

Is it possible to manually create a HTLC using the bitcoin-qt command line? I know how to manually creating createrawtransaction/sendrawtransaction using the bitcoin-qt clients command line, and ...
5 votes
1 answer
226 views

Unilateral close because of HTLC in remote commitment

I run lnd on my node and sometimes see messages like this: [INF] CNCT: ChannelArbitrator(CHANPOINT): immediately failing htlc=HTLCID from remote commitment The corresponding close transaction sent ...
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4 votes
1 answer
330 views

Lightning: why do we need decrementing timelocks in multi-hop payments?

The video (at 28:25) from the official Lightning website describes a multi-hop payment. I understand what a hash-locked contract is, but I still don't understand why we need a timelock aspect here. As ...
4 votes
2 answers
312 views

Why do we need revocation in both the offered/received HTLC outputs and HTLC timeout/success outputs?

The witness script for the output in the HTLC success/timeout transaction is: OP_IF # Penalty transaction <revocationpubkey> OP_ELSE `to_self_delay` OP_CHECKSEQUENCEVERIFY ...
4 votes
1 answer
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What is "Link-Level Multiplexing"?

In a discussion about private channels, Conner Fromknecht mentioned a concept called Link-Level Multiplexing. What is this and what is it useful for? How does it work?
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3 votes
2 answers
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Single-hop Payment vs Multi-hop payments

I am beginner of lightning network. When i am looking roughly lightning network whitepaper, i was confused about the types of contracts used in single-hop and multi-hop. As far as I understand, In ...
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3 votes
1 answer
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Why does every HTLC in a commitment transaction require its own signature?

From BOLT 02 we can learn When a node has changes for the remote commitment, it can apply them, sign the resulting transaction (as defined in BOLT #3), and send a commitment_signed message. 1. type: ...
3 votes
1 answer
102 views

In which cases could I find funds locked in a failed route?

I received an invoice from node Z and my node (A) suggests me 4 possible routes. If the first two routes fail, are there cases in which funds can get stuck in one of these routes until the HTLC ...
3 votes
1 answer
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What Lightning Network transaction information is usable to provide a verifiable public index of received payments?

I have in mind a protocol architecture that includes value transfer, where BTC is the unit of account. To make the protocol scalable I could specify use of the Lightning Network protocol. In this case,...
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3 votes
2 answers
102 views

Why do multihop LN payments start settling from the recipient's end?

In HTLC, after all the parties have locked their funds in the contract, claiming payment happens in a reverse way, starting with the receiver who reveals the preimage of the corresponding payment hash....
3 votes
1 answer
68 views

Difference between capacity and max_htlc in Lightning Network?

What is the difference between capacity and max_htlc in the routing of payments in the network?
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3 votes
1 answer
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How would PTLC's change invoices?

I am wondering how would switching from HTLCs to PTLCs change invoices? I assume there would not be a payment-hash anymore, but what would replace it. A payment-point? Also, is there already support ...
3 votes
1 answer
58 views

Do BIP199's HTLCs suffer from script malleability?

Do BIP199 HTLCs suffer from sigscript malleability like multisigs do due to OP_CHECKMULTISIG?
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3 votes
1 answer
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Lightning Network state deprecation secret keeping

When using a lightning channel, two sides are sending transactions representing the current state (or balance) between them, and for each state sent, they invalidate the previous state by sending a ...
2 votes
1 answer
168 views

Possible race condition(double spend) on HTLC-Timeout in the lightning network?

From the offered HTLC Outputs, # To remote node with revocation key OP_DUP OP_HASH160 <RIPEMD160(SHA256(revocationpubkey))> OP_EQUAL OP_IF OP_CHECKSIG OP_ELSE <remote_htlcpubkey> ...
2 votes
2 answers
594 views

Why do we use CLTV instead of CSV in the HTLC output of the commitment transaction?

In lightning network commitment transactions, the HTLC offered/received outputs generally pay the offering node after a timeout which is scripted using CLTV. In other parts of the commitment ...
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2 votes
1 answer
468 views

Basic questions about lightning network HTLC

I'm reading about lightning and I have a few questions: The HTLC contract seems to be different at each new path payment channel is opened (due to a different Hash value that needs to be provided), ...
2 votes
1 answer
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settling timelocked contracts based on amount of time elapsed in Lightning network

Suppose in a payment route A->B->C, A desires to pay 0.01 BTC to C. It locks in 0.01 BTC with B in the HTLC having timeout period of say 2 days and B locks 0.01 BTC with C in HTLC having timeout ...
2 votes
1 answer
186 views

Remote node signature for HTLC-success and HTLC-timeout transactions

According to BOLT #3, when constructing a HTLC output in the version of the local node (both received and offered HTLC), it requires that the payment to the local node is locked with CHECKMULTISIG ...
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2 votes
1 answer
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Lightning Network: hashlocks vs private keys exchange

I am reading the Lightning Network paper and noticed that when describing bidirectional payment channels, the authors used "Breach Remedy transactions" and the exchange of the two parties' private ...
2 votes
1 answer
145 views

HTLCs and commitment transactions

Why commitment transactions can't simply be HTLCs instead of contracts revocable by having the second half of the Revocable Private Key? I mean, why bother to create a Revocable Public Key from two ...
1 vote
2 answers
79 views

What would happen to Bitcoin if GPS/Galileo timing ceased to be available?

According to this web site, the timing from a system like GPS is essential to "financial networks [which] rely on precision timing for synchronization and operational efficiency." Is the ...
1 vote
1 answer
142 views

Taproot PTLC: Non-Multisig partly timelocked spending conditions

(Taproot environment) What I came up with is the following logic: $alice = A; $bob = B; pk($bob) || (pk($alice) && older(10)) (See on Minsc). I looked at the generated / resulting Bitcoin ...
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2 answers
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Can someone explain how an HTLC is redeemed?

I'm looking at Bolt 3 in the Lightning rfc. My question is about how a HTLC is redeemed. Example HTLC script for reference: # To remote node with revocation key OP_DUP OP_HASH160 <RIPEMD160(SHA256(...
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1 vote
1 answer
70 views

Security implications of removing CHECKSIG in a test

If I conduct an htlc transaction on testnet that does not include OP_CHECKSIG will it still cost an attacker more than (say) $10 in processing power or storage to subvert my tests? Details: I'm ...
1 vote
1 answer
50 views

Decode script return different value from my relative timelock

I want to lock a UTXO for 90 days. My Binary is: 00000000010000000011101101010011 And my sequence is: 533B40 When I decode the witness script with bitcoin-cli decodescript I can see 4209491. Where ...
1 vote
1 answer
163 views

What is the relation between a Hash Time Lock Contract(HTLC) and a Commitment transaction?

I want to know about what happens to the commitment transactions as the HTLC's are sent and cleared along to peers in a route.
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1 vote
1 answer
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Can eltoo's no-penalty design be exploited by malicious submissions of old state?

Eltoo uses the no-penalty submission mechanism, where the cost for an adversary to submit an old state is the transaction fee. This action seems unprofitable, but if we add HTLC to Eltoo, things seem ...
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1 vote
1 answer
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Is it possible to run a Lightning Network node with multiple entities holding parts of the private key?

What's the technical limitation stopping multiple entities from collectively managing an LN node? I understand all parties (entities that share the Node private key) need to be online to sign routing/...
1 vote
1 answer
140 views

how many htlcs can a lightning channel have pending at a given time

Channels can have pending HTLCs, or even handle multiple payments concurrently. Is there a max number of pending HTLCs a channel can entertain? What is that max, why is it set to that number, and what ...
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1 vote
1 answer
124 views

Who bears the transaction fee for settling HTLC in Lightning Network?

Given a channel that exist between Alice and Bob, where Alice wants to transfer 0.0001 BTC to Bob. Alice makes HTLC payment to Bob contingent to the secret for the payment hash within a timelock of ...
1 vote
1 answer
73 views

Do HTLCs get "carried over" in the subsequent commitment transactions?

With regular commitment transactions, current transaction invalidates the previous one. This is fine, since TXs between A and B in their channel happen one after another. However, HTLCs are sort of ...
1 vote
1 answer
196 views

Do HTLC transactions work today or do they need a new soft-fork?

I thought that HTLCs were just a kind of a script construct that would allow to unlock funds for a period of time, which can be unlocked to anyone that provides the original string that matches the ...
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1 vote
1 answer
248 views

Reuse of payment hash in Lightning Network

Suppose there exist two such payment transfer request: A transfers 1 msat to R via A->B->C->R and S transfers 5 msat to R via S->B->C->R. Let the two HTLCs be formed across both the paths ...
0 votes
1 answer
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UNIX END TIME January 19, 2038 - Will it affect Timelock nLOCKTIME smart contracts past that date?

So UNIX END TIME is January 19, 2038. What will happen then to the btc TX that looks at Unixtime for nLOCKTIME transactions? Will any Locktime transaction past that date, say to 2040 be an issue? Or ...
0 votes
1 answer
42 views

Simulate HTLC in regtest c-lightning

I have three nodes in regtest environment l1, l2, and l3 l1 create a channel with l2 l2 create a channel with l3 l3 create an invoice for l1. l1 can pays it because use the route l1-l2-l3 I presume ...
0 votes
1 answer
199 views

How can I create HTLCs below dust_limit_satoshi in Lightning Network?

BOLT#2 documentation for open_channel message has two points (dust_limit_satoshi and htlc_min_msat) in the data message that I found confusing. Below is the statement related to dust_limit_satoshi: ...
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0 votes
1 answer
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What prevent users from cheating in an HTLC contract

I was reading about HTLC and how Charlie have to create a random number and generates its SHA256 hash that is supposed to be used by Bob in the end to finalize the payment he has received from Alice. ...
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0 votes
1 answer
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Lightning protocol modification for app

I'm currently building a Lightning platform for online sellers. I have found that timing can be very problematic: For example, two people want to buy the last item in stock or a unique item like a ...
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0 votes
1 answer
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Atomicity on HTLC payment chain

I have a doubt about HTLC on a lightning network payment. I have this scenario: Alice wants to pay 100 sats to David using a route she found with Bob and Chad, this would be: Alice -> Bob -> ...
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0 votes
1 answer
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Why, how, and when should an intermediate LN node terminate/resolve its HTLC(s) off-chain?

I once heard an attack against LN, which was called "flood & loot": https://medium.com/blockchains-huji/flood-loot-a-systemic-attack-on-the-lightning-network-5c3dac7bba24 The 3rd step of ...
0 votes
1 answer
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lightning to lightning non custodial swaps [closed]

Do you know the way to freeze funds in lightning tx to implement atomic swap between two independent lightning networks?
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1 answer
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How multiple unfinished payments in single LN channel work?

I think I understand HTLCs, at least if they are on chain. I also have a basic understanding of how off chain channel looks like. I understand it as follows. It is a 2-of-2 multisig transaction ...
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1 answer
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Implement HTLC manually by writing scripts

Is there any way to implement HTLC manually for locking funds in the channels in lightning network for a period of time (by setting intervals) and releasing the funds after the time lock expired using ...
0 votes
1 answer
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Destination address(es) when redeeming an HTLC

Starting from this text at https://en.bitcoin.it/wiki/Script: "The script for a typical Bitcoin transfer to destination Bitcoin address D simply encumbers future spending of the bitcoins with two ...