Controller is a smart contract used by the solver to communicate and command blockchains. A Controller can be thought as a middleware that acts as a translator between various blockchains, in which users can submit requests & task which will be carried out in the respective blockchains.
Smart Contract Address
Do Controller Access My Private Key ?
No Controller Don't need access or ever uses private key, you can command controller using your crypto wallets directly. Your private keys stays on your system.