user61183: We know that escrow mechanisms are easy to implement when it involves a trusted 3rd party. For example if A and B don't trust each other they can simply send their goods to C whom they both trust. Then C can distribute the goods to them fairly.
However, is there a primitive that achieves the same when there isn't a trusted 3rd party? Basically, A and B don't trust each other and they want to exchange something. Can they do this without involving any trusted party?

user38618: There's "Decred cross-chain atomic swapping". It allows two people to exchange cryptocurrencies (currently BTC/LTC/Vertcoin/Decred) without trusting on a third party nor each other.
UPDATE: There's also Lightning Network atomic swap.
You can read about it on Decred blog or Github

61183: <p>We know that escrow mechanisms are easy to implement when it involves a trusted 3rd party. For example if <em>A</em> and <em>B</em> don't trust each other they can simply send their goods to <em>C</em> whom they both trust. Then <em>C</em> can distribute the goods to them fairly.</p>

<p>However, is there a primitive that achieves the same when there isn't a trusted 3rd party? Basically, <em>A</em> and <em>B</em> don't trust each other and they want to exchange something. Can they do this without involving any trusted party?</p>
 38618: <p>There's "Decred cross-chain atomic swapping". It allows two people to exchange cryptocurrencies (currently BTC/LTC/Vertcoin/Decred) without trusting on a third party nor each other.</p>

<p>UPDATE: There's also Lightning Network atomic swap.</p>

<p>You can read about it on <a href="https://blog.decred.org/2017/09/20/On-Chain-Atomic-Swaps/" rel="nofollow noreferrer">Decred blog</a> or <a href="https://github.com/decred/atomicswap" rel="nofollow noreferrer">Github</a></p>
