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1  Bitcoin / Development & Technical Discussion / Re: Trying to get a deeper understanding of atomic swaps on: October 09, 2018, 08:07:07 PM
I'm very sorry, that I was not able to translate it within a few days as I planned... And as it seems atm, it will take a few more weeks, as I have a lot on my table right now...

I hope to get it done this year, but I won't make any promises. Sorry Sad
2  Bitcoin / Development & Technical Discussion / Re: Trying to get a deeper understanding of atomic swaps on: September 21, 2018, 11:55:41 AM
I will start translating it today. Maybe I get it done this weekend. My thesis starts at the very beginning, so I hope even people who are not familiar with atomic swaps can under stand it.

As this is a thesis to a unimportant module in my course of studies, it was not peer reviewed and also not published (besides my personal git repo).

I will take a look at the homomorphic hashing stuff, this seems interesting, thanks.
3  Bitcoin / Development & Technical Discussion / Re: Trying to get a deeper understanding of atomic swaps on: September 21, 2018, 10:31:49 AM
Hi together,

I finished my thesis now and have some results.

I put everything I accomplished in a git repo, so everybody can view my results. At the moment there is only the german thesis, but I will try to translate it within the next days.

I hope my work is usefull to somebody.

Git: https://github.com/noobWithAComputer/detect-atomic-swaps

Greetings.
4  Bitcoin / Development & Technical Discussion / Re: Trying to get a deeper understanding of atomic swaps on: July 23, 2018, 07:54:24 PM
Thank you all for your thoughts. Especially to Kallisteiros for your long post.

You are right about the swapped parameters in Type 4a/b and 6.

@mr_sparkles
I will look into it. This might be interesting.
5  Bitcoin / Development & Technical Discussion / Re: Trying to get a deeper understanding of atomic swaps on: July 20, 2018, 09:41:43 AM
Interesting, thank you for these information.

I just checked the HTLCs I found and there was none in Dec 2017. So it seems the LN HTLCs have another structure. I will take a deeper look into this in the next days.
6  Bitcoin / Development & Technical Discussion / Re: Trying to get a deeper understanding of atomic swaps on: July 19, 2018, 09:53:06 AM
When I find the time to translate my work (I'm writing the thesis in german), I will post them here.

As I will start my Diplom thesis in a few months, I won't have the time to implement such a tool. But I hope my findings may help other people to do so.
7  Bitcoin / Development & Technical Discussion / Re: Understanding Atomic Swaps on: July 16, 2018, 02:21:37 PM
The concept of an atomic swap is not a part of the lightning network.

It's just a structure of transactions utilizing hashed timelock contracts (HTLCs) in order to achieve a trustless exchange of different currencies on different chains. Until now multiple atomic swaps were made on bitcoin.
ATM I'm writing a thesis about atomic swaps and how to recognize them. There are a few different scripts for HTLCs, but they all do the same thing: they lock value for a specific time, except the counterparty can provide the preimage of the given hash.

One implementation of an HTLC looks like this:
Code:
63	if
82	size
01	data1
	20
88	equalverify
a8	sha256
20	data32
	<secret_hash 32byte>
88	equalverify
76	dup
a9	hash160
14	data20
	<pubkey_hash1 20byte>
67	else
04	data4
	<timelock 4byte>
b1	checklocktimeverify
75	drop
76	dup
a9	hash160
14	data20
	<pubkey_hash2 20byte>
68	endif
88	equalverify
ac	checksig

In order to have an atomic swap you just need an implementation which achieves the same thing. In ethereum you could also write a smart contract which does the same. As far as both parties can watch the blockchain and what is happening there, it is possible to make an atomic swap.
8  Bitcoin / Development & Technical Discussion / Trying to get a deeper understanding of atomic swaps on: July 16, 2018, 12:43:59 PM
Hi together,

I'm an IT-student and writing a thesis about atomic swaps on BTC and BTC-like blockchains. For the thesis I decided to use BTC, LTC, BCH and DCR. These chains have a somehow similar codebase and the same scripting language (I'm not a professional, so there might be differences, but they are not that serious). And they all have a high enough marketcap to be relevant for atomic swaps.
So the goal of the thesis is to find hashed timelock contracts (HTLCs) and connect matching HTLCs from different chains to get the atomic swap. Therefore I first searched the web for anything on atomic swaps [1] and analyzed the input script of this transaction [2] to get a basic understanding how atomic swaps work and what they look like.
Then I wrote a go program to search for any script longer than simple P2PKH scripts. This gave me a list of many different scripts which I analyzed by hand to only take the HTLC ones. (Besides many multisig scripts, there is not much to find on BTC^^)
At this point I found multiple different types of HTLCs as listed below. Afterwards I crawled* BTC again saving all transactions with HTLC scripts, storing the interesting data like tx-id, input value, pubKeyHashes, the secrets and their hashes. I found about one hundret HTLCs on BTC so far.
I did the same for LTC and found about 400 HTLCs.
As far as I understood, the secrets of HTLCs have to be the same on both chains. So I wrote another go program to match the found HTLCs from BTC and LTC and got around 30 matches. The next steps would then be to crawl BCH and DCR and also match the HTLCs found there.

* Crawling in this case means that I start to search the blockchain backwards (to get the newest first, the beginning years are not that interesting in this case^^) until the beginning of 2017. So about 18 months. As stated in [1] the first known atomic swap between BTC and LTC was made on 19th April 2017 (or April 19th 2017 or 19.4.2017 or whatever you like). So there is not much sense in crawling any further.

My questions now are the following:

  • Why are there so many different types? Is it compatibility with other chains? Or what?
  • What are the differences between these types (besides length and hashing algorithm)?
  • What are the advantages and disadvantages of these types?
  • Why are there so many HTLCs on LTC and so few on BTC?
  • Do you know other such HTLC scripts?
  • Can you provide interesting resources on this topic?

I'm open to any constructive input and hope you have a few answers for me. Thank you in advance.

Type 1: sha256 secret, length=97byte
Code:
63	if
82	size
01	data1
	20
88	equalverify
a8	sha256
20	data32
	<secret_hash 32byte>
88	equalverify
76	dup
a9	hash160
14	data20
	<pubkey_hash1 20byte>
67	else
04	data4
	<timelock 4byte>
b1	checklocktimeverify
75	drop
76	dup
a9	hash160
14	data20
	<pubkey_hash2 20byte>
68	endif
88	equalverify
ac	checksig

Type 2a: sha256 secret, length=94byte
Code:
63	if
a8	sha256
20	data32
	<secret_hash 32byte>
76	dup
a9	hash160
14	data20
	<pubkey_hash1 20byte>
88	equalverify
ac	checksig
67	else
04	data4
	<timelock 4byte>
b1	checklocktimeverify
75	drop
76	dup
a9	hash160
14	data20
	<pubkey_hash2 20byte>
88	equalverify
ac	checksig
68	endif

Type 2b: sha256 secret, length=93byte
Code:
63	if
a8	sha256
20	data32
	<secret_hash 32byte>
88	equalverify
76	dup
a9	hash160
14	data20
	<pubkey_hash1 20byte>
67	else
04	data4
	<timelock 4byte>
b1	checklocktimeverify
75	drop
76	dup
a9	hash160
14	data20
	<pubkey_hash2 20byte>
68	endif
88	equalverify
ac	checksig

Type 3: ripemd160 secret, length=81byte
Code:
63	if
a6	ripemd160
14	data20
	<secret_hash 20byte>
88	equalverify
76	dup
a9	hash160
14	data20
	<pubkey_hash1 20byte>
67	else
04	data4
	<timelock 4byte>
b1	checklocktimeverify
75	drop
76	dup
a9	hash160
14	data20
	<pubkey_hash2 20byte>
68	endif
88	equalverify
ac	checksig

Type 4a: hash160 secret, length=86byte
Code:
63	if
03	data3
	<timelock 3byte>
b1	checklocktimeverify
75	drop
76	dup
a9	hash160
14	data20
	<pubkey_hash2 20byte>
88	equalverify
ac	checksig
67	else
76	dup
a9	hash160
14	data20
	<secret_hash 20byte>
88	equalverify
ad	checksigverify
82	size
01	data1
	21 -> 33
88	equalverify
a9	hash160
14	data20
	<pubkey_hash1 20byte>
87	equal
68	endif

Type 4b: hash160 secret, length=82byte
Code:
63	if
03	data3
	<timelock 3byte>
b1	checklocktimeverify
75	drop
76	dup
a9	hash160
14	data20
	<pubkey_hash2 20byte>
88	equalverify
ac	checksig
67	else
76	dup
a9	hash160
14	data20
	<secret_hash 20byte>
88	equalverify
ad	checksigverify
a9	hash160
14	data20
	<pubkey_hash1 20byte>
87	equal
68	endif

Type 5a: hash160 secret, length=81byte
Code:
63	if
a9	hash160
14	data20
	<secret_hash 20byte>
88	equalverify
76	dup
a9	hash160
14	data20
	<pubkey_hash1 20byte>
67	else
04	data4
	<timelock 4byte>
b2	checksequenceverify
75	drop
76	dup
a9	hash160
14	data20
	<pubkey_hash2 20byte>
68	endif
88	equalverify
ac	checksig

Type 5b: hash160 secret, length=78byte
Code:
63	if
a9	hash160
14	data20
	<secret_hash 20byte>
88	equalverify
76	dup
a9	hash160
14	data20
	<pubkey_hash1 20byte>
67	else
01	data1
	<timelock 1byte>
b2	checksequenceverify
75	drop
76	dup
a9	hash160
14	data20
	<pubkey_hash2 20byte>
68	endif
88	equalverify
ac	checksig

Type 6: hash160 secret, length=79byte
Code:
63	if
54	<timelock op>
b1	checklocktimeverify
75	drop
76	dup
a9	hash160
14	data20
	<pubkey_hash2 20byte>
88	equalverify
ac	checksig
67	else
76	dup
a9	hash160
14	data20
	<secret_hash 20byte>
88	equalverify
ad	checksigverify
a9	hash160
14	data20
	<pubkey_hash1 20byte>
87	equal
68	endif

Type 7: multiple ripemd160 secrets, length=80 + n*23byte
Code:
63	if
a6	ripemd160
14	data20
	<secret_hash1 20byte>
88	equalverify
a6	ripemd160
14	data20
	<secret_hash2 20byte>
...
88	equalverify
a6	ripemd160
14	data20
	<secret_hash_n 20byte>
88	equalverify
21	data33
	<signature1 33byte>
ac	checksig
67	else
04	data4
	<timelock 4byte>
b1	checklocktimeverify
75	drop
21	data33
	<signature2 33byte>
ac	checksig
68	endif

Type 8: multiple ripemd160 secrets, length=81 + n*23byte
Code:
74	depth
60	16
87	equal
63	if
a6	ripemd160
14	data20
	<secret_hash1 20byte>
88	equalverify
a6	ripemd160
14	data20
	<secret_hash2 20byte>
...
88	equalverify
a6	ripemd160
14	data20
	<secret_hash15 20byte>
88	equalverify
21	data33
	<signature1>
67	else
03	data3
	<timelock 3byte>
b1	checklocktimeverify
75	drop
21	data33
	<signature2>
68	endif
ac	checksig

[1] http://www.cryptovibes.com/crypto-news/charlie-lees-atomic-swap-between-litecoin-and-bitcoin-was-a-success/
[2] https://insight.bitpay.com/tx/0bb5a53a9c7e84e2c45d6a46a7b72afc2feffb8826b9aeb3848699c6fd856480
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