interface NavVerifier {

    /// @dev Verifies that a signature is valid.
    /// @param sellPrice Price in wei
    /// @param buyPrice Price in wei
    /// @param signaturevaliduntilBlock Number of blocks till price expiry
    /// @param hash Message hash that is signed.
    /// @param signedData Proof of nav validity.
    /// @notice mock function which returns true
    function isValidNav(
        uint256 sellPrice,
        uint256 buyPrice,
        uint256 signaturevaliduntilBlock,
        bytes32 hash,
        bytes signedData)
        external
        view
        returns (bool isValid);
}
function isValidNav(
    uint256 sellPrice,
    uint256 buyPrice,
    uint256 signaturevaliduntilBlock,
    bytes32 hash,
    bytes signedData)
    external
    view
    returns (bool isValid);

/// @dev Verifies that a signature is valid.
/// @param sellPrice Price in wei
/// @param buyPrice Price in wei
/// @param signaturevaliduntilBlock Number of blocks till price expiry
/// @param hash Message hash that is signed.
/// @param signedData Proof of nav validity.
/// @notice mock function which returns true