Slippage Rate Protection
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You are referring to the Legacy version of KyberSwap docs.
For the most updated information, please refer to:
The token conversion rate varies with different source token quantities. It is important to highlight the slippage in rates to the user when dealing with large token amounts. We list some methods on how this can be done below.
Call getExpectedRate for 1 ETH equivalent worth of srcToken.
Call getExpectedRate for actual srcToken amount.
If the obtained rates differ by a defined percentage (either in the smart contract, or as a user input), reject the transaction.
An example of how this could be done is shown above. How the rate slippage is calculated is as follows:
Call getExpectedRate for 1 ETH equivalent worth of srcToken.
Call getExpectedRate for actual srcToken amount.
Calculate the rate difference and display it prominently in the user interface.
maxDestAmountIn the case where maxDestAmount is being used, beware of slippage rates when maxDestAmount is significantly lower than srcQty. We give an example below.
Users wants to swap for a maxDestAmount of 3000 DAI, but specifies a srcQty of 300 ETH.
Kyber will search the best rate for the srcQty of 200 ETH, but the rate might be significantly worse than rates for lower srcQty. For example, the user gets a rate of 1 ETH = 100 DAI, while he could have gotten a better rate of 1 ETH = 200 DAI if he specified a lower srcQty.
Kyber will use the rate to calculate the amount necessary for 2900 DAI, and refund the rest of the unused ETH back to the user. In the case mentioned above, 30 ETH will be used, and the remaining 270 ETH returned to him. He could have instead needed just half that amount (15 ETH) had he specified a lower srcQty instead.
In summary, if srcQty is significantly larger than maxDestAmount, the user could potentially be forced to trade with significantly worse rates.
