Adding support for LTC or other currencies in BTC?

[shade_tom]

Has there been an attempt at adding LTC or any other cryptocurrencies to BTC or another altcoin? Specifically I intend to trade crypto-crypto without an exchange.

I propose a simple scheme, all nodes sync the blockheaders similar cryptocurrencies, taking up a trivial amount of space, and a new opcode is added to BTC to verify that a specific block exists within a specific blockchain.
This would allow for the following transaction to take place:

Suppose Alice wants to trade 10 BTC for Bob's 10 LTC:

• Bob crafts an LTC transaction to send 10 LTC to Alice's LTC wallet.
• Bob does not broadcast this to the chain, but sends an unsigned version to Alce
• Alice creates a BTC tx to allow Bob to spend 10 BTC on condition that Bob's transaction to Alice exists on the LTC blockchain
• Alice publishes her transaction to the BTC blockchain
• Bob can spend the transaction that Alice sent if he can prove that a specific block on the LTC chain contains the Tx that he sent Alice
• Therefore, Bob must publish his transaction to the LTC blockchain

Obviously, one would need a timeout condition, e.g. allow Alice to spend the BTC if it has been over a day, otherwise Bob could simply burn Alice's BTC by never sending Alice 10 LTC on the LTC network.

Any thoughts or insights?

[ImHash]

I have some thoughts, why wouldn't they get married and let us be? that way there is no need for transactions at all
Then if swapping was available how to calculate the price difference? I mean then we would be needing a source to determine both prices, that's when exchanges play their roles, if they can't then no business for them, and trading will become unprofitable and coins crash.

[shade_tom]

To calculate price differences on-chain one could generalize the first example to make a psuedo-exchange.

That is, have a bunch of coins on the BTC blockchain that are only spendable if coins go to a specific address on a separate chain.
That way the BTC/LTC price would simply be how low someone is willing to sell their BTC for in exchange for LTC.
I do however see a problem with divisibility here... I have to do some more thinking to figure that out.

[pooya87]

(let me just first admit that i am not completely familiar with the process because i have never read details about it.)

there is this thing called Lightning Network coming and it has a lot of features, one of them is called Atomic Swap. i believe it uses something like smart contracts or multisig to allow all cryptocurrencies with Lightning Network to do this Swap or exchange completely decentralized.

you may want to research the term and find out more yourself.

Edit: a link: https://en.bitcoin.it/wiki/Atomic_cross-chain_trading