Unrelated to atomic swaps. In a nutshell you burn Syscoins on the SYS blockchain and then use the the resulting proofs from that to mint SYSX ERC20 on the ETH chains through a series of contracts that validate the proof using SPV.

A few terms to be aware of:
Superblock chain (contract) - A two way sidechain between SYS and ETH. 'Agents' collect 60 minutes worth of block headers from the Syscoin chain and post them to a superblock contract on the Ethereum chain. Data from the superblock contract is used to validate proof-of-burn from the Syscoin chain using SPV proofs.
Agents - Nodes that are bonded by 3 ETH and are responsible for submitting SYS block headers to the superblock contract on ETH. These nodes are also responsible for challenging other's who are submitting block headers that do not match their own. This mismatch initializes a challenge/response game between the two. The loser loses their ETH. Agents also earn SYS ERC20 (SYSX) for submitting superblocks. They earn fees for all assets moving across the bridge.
Syscoin Relayer - A process that runs adjacent to syscoind and relays blocks from a local geth client to syscoin. This data is used to validate proof-of-burn from the Ethereum chain coming back to Syscoin using SPV.


There are probably multiple points of attack but i think the biggest opportunities, if any, would be in:
- Submitting bad data to the superblock contract and it not being challenged/declined by other agents
- The challenge response game in itself; DDoS of other agents, or other vectors in there.
- The Syscoin relayer, tricking it somehow maybe?

Code
https://github.com/syscoin/syscoin
https://github.com/syscoin/sysethereum-contracts
https://github.com/syscoin/sysethereum-dapp
https://github.com/syscoin/sysethereum-agents


Happy hacking

Hey hadarian,

Thanks for the questions.

You can checkout more information of the bridge here

But basically the bridge is a connection between Syscoin Assets and Ethereum ERC-20 tokens performed via a minting/burning process crosschecked by agents and validators, making it a trustless swap without any third-parties or P2P like atomic swaps. This enables ERC-20 tokens to come over to Syscoin and use it's protocol, and allows Syscoin Assets to move to ETH ERC-20 tokens to use it's protocol.

In a minting/burning fashion, the total supply will never increase/decrease, merely move between both chains.
For eg.
You have ERC20 token called CATS with 100k supply and you want to move over to Syscoin to use it's assets and Z-DAG(Zero Confirmation Transactions). You burn 50k(any amount) ERC20 + a fee, and move across to a Syscoin Asset called CATS. You will now have a 50k Supply on ERC-20 and a 50k supply on Syscoin side totalling the 100k. Then the same goes for moving back to ETH chain. You burn the 50k from SYS assets and move to the ETH ERC-20 side where CATS ERC20 is then minted again, bringing the ERC-20 supply back to 100k and Sys asset supply of CATS to 0.