What are the Requirements of Atomic Swaps?

As exciting as this technology is, there are some fundamental requirements for a cryptocurrency before it can successfully support atomic swaps. One such requirement is the implementation of the Lightning network.

If a hash time-locked contract can be thought of as linking two blockchains together, the lightning network can be thought of as linking payment channels together. That is, for Alice and Bob to transact with each other, they must be linked through payment channels. The lightning network allows for that.
In addition, for a transaction to occur between two different blockchains, it is necessary for both blockchains to share the same cryptographic hash function, such as SHA-256. This is to allow for the hash-time locked contract to function properly when it comes to the user providing the number that was generated via the hash function.