Smart Contracts can be written in:

Solidity, Viper, LLL and Serpent, because those are high level languages that are compiled down to bytecode.

Java, C++, Solidity and JavaScript, because the Ethereum Blockchain is completely language agnostic and cross compilers exist for every major language.

Solidity, Viper, LLL and Serpent, because those are high level languages that are compiled down to bytecode.

Solidity and JavaScript, because those are the official first implementations for Distributed applications and the Blockchain supports those languages fully.

Solidity gets compiled:

to bytecodes which are essentially opcodes running instruction by instruction.

to bytecode that can't be understood by humans.

to bytecodes which are essentially opcodes running instruction by instruction.

Having a bug-bounty program early on:

can help to engage the community in testing your smart contracts and therefore help to find bugs early.

might be a burden as it is an administrative overhead mainly.

is completely useless. Who wants to test beta-ware software? It’s better to start with the bug-bounty program after the contract is released on the main-net.

Which is the right order for Denominations?

Wei, Finney, Szabo, Ether, Tether.

The nonce-field in a transaction is used:

to protect against replay attacks.

to have an additional checksum for transactions.

to sum up all ethers sent from that address.

Which statement is true about the EVM?

The EVM is extremely powerful, turing complete and perfect for doing computational intensive things, because of the direct access to the graphics card.

While the EVM is Sandboxed, it isn't as powerful as the Bitcoin Network, because it's not Turing Complete.

The EVM can't access hardware layers or anything outside a blockchain node because it's sandboxed.

The EVM is extremely powerful, turing complete and perfect for doing computational intensive things, because of the direct access to the graphics card.

an amazing way to create new applications. Those applications run entirely separated from other applications on the platform and allow for logical interactions. They can't access any funds to add an additional layer of trust.

great, because they cut the middle man, run on a trusted platform, apply logic to the blockchain where already economic assets are running and thus allow peer to peer trade.

an amazing way to create new applications. Those applications run entirely separated from other applications on the platform and allow for logical interactions. They can't access any funds to add an additional layer of trust.

a new way of applying logical operations for banks and big financial institutions. This way they can reduce the staff while operating at increased security.

To get most out of the blockchain, it is best:

to use it only for things which need the benefits of the blockchain.

to use it for the whole business logic. It’s always best to have everything in once place.

to use it only for things which need the benefits of the blockchain.

A Hashing Algorithm is deterministic. What does it mean?

it always produces the same output given the same input.

it uses equally distributed data to produce the output given a long input.

it shouldn't be possible to re-generate the input given the output.

What's the correct scientific notation?

1 Ether = 10^18 wei, 10^9 Gwei, 10^3 Finney

1 Ether = 10^19 wei, 10^13 Gwei, 10^3 Finney

1 Ether = 10^16 wei, 10^13 Gwei, 10^3 Finney

1 Ether = 10^18 wei, 10^6 Gwei, 10^6 Finney

What are Private Keys used for?

To Sign Transactions And To Derive an Address From.

To Protect the Public Keys by being cryptographically significant.

To Sign Transactions And To Derive an Address From.

To Generate An Address which can sign transactions.

Public Keys vs. Private Keys. Which statement is true?

The Private Key signs transactions, the Public Key can verify the signature.

The Public Key is for Signing Transactions, the Private Key must be given out to verify the signature.

The Private Key signs transactions, the Public Key can verify the signature.

The Private Key is to generate a Public Key. The Public Key can sign transactions, the address is here to verify the transactions.

Proof of Work (PoW) vs. Proof of Stake.

PoW is computationally intensive which requires lots of energy. On the other hand, miners earn straightforward a reward for mining a block and incorporating transactions.

PoW is better than PoS, because with PoS we increase the amount of energy spent on the network.

PoS is mining with specialized new hardware that has to be purchased with a stack of Ether in the network. Hence the Name: Proof of Stake, which derives from Stack.

Externally Owned Accounts:

are bound to a private key which is necessary to sign transactions outgoing from that account.

can be destroyed using the selfdestruct keyword. This way all remaining ether will be sent to the receiver address, regardless if they have a fallback function or not.

are bound to a private key which is necessary to sign transactions outgoing from that account.

are logical opcodes running on the ethereum blockchain very similar to smart contracts.

are sitting on their own address. The Address is created from the nonce and the EOA address and could be known in advance before deploying the smart contract.

are always living on the same address, because the blockchain is deterministic. So, one account can always have one smart contract.

are having the same address as the EOA.

are sitting on their own address. The Address is created from the nonce and the EOA address and could be known in advance before deploying the smart contract.

the address of the smart contract is a random address which gets generated by the miner who mines the contract-creation transaction.

Transactions containing the same data to create the same smart contract are:

having a different signature because of the nonce which changes upon every transaction.

always having the same signature.

having a different signature because of the nonce which changes upon every transaction.

Sending one Ether is actually internally translated:

to Wei, so it will send the equivalent of 10^18 Wei.

to Finney, so it will send the equivalent of 10^3 Finney.

to Szabo, so it will send the equivalent of 10^6 Szabo.

the Dagger-Hashimoto hashing while internally the EVM uses Keccack256 which is almost similar to SHA256, but has a different padding so produces different hashes.

Keccack256 while internally to hash values it's easy to use the Dagger-Hashimoto to create a meaningful hash.

the Dagger-Hashimoto hashing while internally the EVM uses SHA256 which is an alias for Keccack256.

the Dagger-Hashimoto hashing while internally the EVM uses Keccack256 which is almost similar to SHA256, but has a different padding so produces different hashes.

would be better, because it can reduce the amount of energy needed for mining.

would be worse, because it would increase the amount of energy needed for mining.

Externally Owned Accounts (EoA):

are changing their address every time a Transaction is sent because of the nonce.

are keeping their address, but on the blockchain a nonce is increased every time they send a transaction to avoid replay attacks.

What are Ethereum Nodes?

Programs implementing the Ethereum Protocol to talk to each other and JSON-RPC interfaces to talk to the outside world.

A Java-Script library to compile and run Solidity Code.

A Framework for deploying and running smart contract in a decentralized way.

To communicate with an Ethereum node via JavaScript:

the library you use must make use of the JSON-RPC Interface of an Ethereum Node.

must Implement the Ethereum Protocol to connect to other Ethereum Nodes.

must use Web3.js, which is closed source to communicate to other Ethereum Nodes.

It’s possible to access the blockchain via an Ethereum Node:

by any programming language, as long as it adheres to the JSON-RPC standard.

only via JavaScript because there is the proprietary Web3.js library.

by any programming language, as long as it adheres to the JSON-RPC standard.

A Private Network is:

a Network running only in a private area, where people cannot join freely and openly.

a side Channel to the Ethereum Main Net which costs less gas to run smart contracts.

an exact clone of the Rinkeby Test-Network which can be started as virtual machine in the Azure Cloud.

a Network running only in a private area, where people cannot join freely and openly.

For Rapid Development Cycles it's good:

to use in-memory blockchain simulations, because mining works instantaneously.

to deploy to the main-network as quickly as possible.

to use in-memory blockchain simulations, because mining works instantaneously.

to use a private network at all times, because this is the closest you get to the real network.

Go-Ethereum vs. Ganache:

with Go-Ethereum you get a real blockchain node where you can create your own local private network, connect to Test-Networks or the Main-Net, while with Ganache you get an in-memory blockchain simulation.

both are the same, just implemented in a different language.

with Go-Ethereum you get a real blockchain node where you can create your own local private network, connect to Test-Networks or the Main-Net, while with Ganache you get an in-memory blockchain simulation.

with Ganache you get a real blockchain node where you can connect to the Test-Networks Rinkeby and Ropsten.

the timestamp can be influenced by a miner to a certain degree but it's always independent from the time-zone.

the timestamp is based on the time zone of the miner, that is why it changes the difficulty continuously to reflect network latency.

the timestamp can't be influenced by a miner and is generally considered safe to be used for randomness on the blockchain.

the timestamp can be influenced by a miner to a certain degree but it's always independent from the time-zone.

increases when the time between mined blocks is below 10 seconds, while it decreases when the time is above 20 seconds.

is determined by the Ethereum Committee every fortnight to reflect the average amount of transaction and it cannot be influenced by the network itself.

increases when the time between mined blocks is below 10 seconds, while it decreases when the time is above 20 seconds.

increases when the time between mined blocks is below 20 seconds, while it decreases when the time is above 60 seconds.

must implement the Ethereum Protocol and a JSON-RPC to talk with clients.

must implement the Ethereum protocol and external access can only be done via the proprietary Ethereum Libraries like Web3.js.

must implement the Ethereum Protocol and a JSON-RPC to talk with clients.

must implement Web3.js to interact with Websites.

When a new block is mined:

a list of transactions as well as uncles is incorporated in the block. All gas that is used during those transactions is added to the miners' balance. Also, the block reward is added to the miner. Then the same transactions are run again byevery participating node in the network to achieve consensus.

a list of transactions is incorporated in that block. Gas used during the execution is attached to the executing contracts while the block reward is automatically spread across the mining pool to ensure a fair spread. Consensus is reachedby a special form of hash code.

can become a mining node, depending if the implementation has the functionality implemented.

can never become a mining node.

can always become a mining node.

can become a mining node, depending if the implementation has the functionality implemented.

On a consortium network:

usually only a few selected nodes can be miners. Transactions can be further limited.

everybody can become a miner, everybody can send transactions and everything is public.

usually only a few selected nodes can be miners. Transactions can be further limited.

The JSON-RPC Protocol:

is used to communicate between the blockchain node and externally running applications.

is used to communicate between blockchain nodes.

is used to ensure safe communication between miners.

is a mean of dumping the blockchain data in a so-called consensus export.

is used to communicate between the blockchain node and externally running applications.

is one of the many blockchain nodes that implement the Ethereum Protocol. It's open source and everyone can contribute.

is the reference implementation of the Ethereum protocol and every other node implementation internally uses the closed-source from Geth.

is the library that is used for the blockchain node Go-Ethereum. It is also used by Parity is parts, because it's closed source.

is one of the many blockchain nodes that implement the Ethereum Protocol. It's open source and everyone can contribute.

To store almost all data in the Ethereum Blockchain:

a Merkle Patricia Trie is used.

a Linked List with pointers to previous blocks hashes is used.

a Merkle Patricia Trie is used.

a Radix Trie is used because the Merkle Patricia Trie is too inefficient.

Checking the balance of an address inside a loop of a smart contract constantly:

cost gas every time we check the balance.

Gas costs accrue on sending a transaction:

only with a new smart contract deployment.

only interacting with an already deployed smart contract.

can be split across multiple files, but every contract must be in a file with the same name as the contract itself.

is much better than Solidity and a viable alternative.

can be split across multiple files, but every contract must be in a file with the same name as the contract itself.

is another language similar to LLL, more secure than Solidity.

Blockchain CBDE Practice Test 1 - Free Online Exam Questions 1-40

Consensus is reached:

by the miner nodes which make sure that a transaction is valid.

by every single node in the blockchain network executing the same transaction.

by a cryptographic secure signature algorithm called ECDSA which makes sure that cheating is impossible.

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