Briefly introduced are smart contracts and what makes them attractive. In addition, Etherparty | Making Smart Contracts Smarter gives a glimpse as to how their vulnerabilities when deducted can be used to secure them better in the future.
A smart contract
In definition, smart contracts can be identified by their unique address – a 160-bit identifier. A smart contract is evoked when sending a cryptocurrency payment to a certain contact address. Once a new transaction gets accepted by the blockchain, it gets a new recipient contact address. From here all the parties on the mining network transaction execute this contract code using the current state of blockchain and their transaction payloads during input. Your network then participates in a consensus pool as it determines the next states output.
In Ethereum, specially created transaction contracts are introduced to the blockchain. A contract in the real sense is an Ethereum Virtual Machine byte-code function that gets incorporated into the blockchain as the transaction is being created. You can have the contract written in higher level language as it is compiled as an EVM bytecode. The contract functions offer private storage on the blockchain and can store a certain amount of virtual Ether coins. The area of private storage can be initialized when running a constructor. This means subsequent transactions invoke the anonymous function when transactions are relayed to a certain contract address.
What are the vulnerabilities of the smart contract?
We have debunked that the smart contracts are vulnerable to attacks due to their high-value aspect. Additionally, they possess some features that any experienced software guru should consider keenly. One, they operate in anonymous networks where they do not have to request for permission to run. Any participant can join them. Secondly, callers or miners have a great deal of control over the environments in which their transactions are executed.
This covers which transactions are best for execution and which transcripts are best for accepting, ordering, setting up time stamps and manipulating call stacks. Finally, all the vulnerabilities mentioned above can punish anyone who is unable to navigate their way right at the onset. Unfortunately, there is no mechanism for patching a smart contract regardless of how much money it contains.
Things to consider
It’s possible to design or upgrade your smart code contract as all contract can call each other. However, the original bytecode used by the contract remains immutable forever. The vulnerabilities can be simply summed up into time stamp dependence, reentrancy vulnerability, transaction-ordering dependence and mishandled exceptions.
Miners are capable of controlling the order in which transactions get executed. This means that certain contracts are influenced by users in that they might not match the contract at the time the transaction is executed if another transaction updates it.
How protect smart contracts?
The best proposal forward is to allow a guard clause that does an evaluation before your transaction is executed. If evaluation comes out false, the transaction does not get executed. With this information, you can come up with your own concurrency scheme.