When you are making a payment with an ERC20 token like TRST or DAI you need to sign TWO transactions.
Here's how it works
- Let's say, for example, you intend to contribute 1 TRST to a lending circle smart contract.
- You will be asked to sign two transactions
- The first transaction: Tell the Trustcoin smart contract that maintains the TRST token that you approve of the transfer of 1 TRST to the lending circle.
- The second transaction: Tell the smart contract of the lending circle to make the transfer of the 1 TRST from your ETH address to the circle's ETH address.
Note: Both of these transactions will require gas, paid in Ethers.