LOCUS CHAIN security record

The function `transferFrom` deviate from the `ERC20` standard and does not emit `Approval` event for the changed allowance.

Two declarations do not conform to the [Solidity style guide](https://solidity.readthedocs.io/en/v0.7.3/style-guide.html#naming-conventions) with regards to its naming convention. Particularly: - `camelCase`: Should be applied to function names, argument names, local and state variable names, modifiers - `UPPER_CASE`: Should be applied to `constant` variables - `CapWords`: Should be applied to contract names, struct names, event names and enums

The functions which are never called internally within the contract should have external visibility for gas optimization.

```solidity=67 function approveAndCall(address _spender, uint _value, bytes _extraData) public returns(bool) { ``` - The function `approveAndCall` implicitly returns a default value.

Functions that update state variables should emit relevant events as notifications.

The **require** statement can be used to check for conditions and throw an exception if the condition is not met. It is better to provide a string message containing details about the error that will be passed back to the caller.

The cited address input is missing a check that it is not `address(0)`.

Current Locus implementation is vulnerable to [a known ERC20 race condition issue](https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729), which could lead to token theft. When a user calls `approve()` for a second time on a spender that has already been allowed, the spender could call `transferFrom()` to transfer the previous value and still receive the authorization to transfer the new value. Exploit scenario: 1. Alice calls `approve(Bob, 100)` to allow Bob to spend 100 tokens. 2. Alice changes her mind and calls `approve(Bob, 50)`. 3. Bob observes the second `approve(Bob, 50)` function call and calls `transferFrom(Alice, Bob, 100)` before the second `approve(Bob, 50)` call. 4. The above scenario can be achieved by front-running. In this case, Bob can transfer another 50 tokens from Alice and in total, he transferred 150 tokens from Alice.

The highlighted `if` statement will always equal `true` because the `approve()` function either reverts or returns true.

Literals with many digits are difficult to read and review. ```solidity=15 uint internal constant initialSupply = 7000000000 * (10 ** uint(decimals)); ```