Ethereum Developer Test 1

Question 1

Among the Ethereum addresses, public keys, and private keys, which statement is TRUE?

Accepted Answer

An address is 20 bytes long, a public key is 64 bytes and the private key is 32 bytes

Answer

In Ethereum's cryptographic architecture, a private key is a 32-byte (256-bit) random number. From this private key, a 64-byte (512-bit) public key is derived using elliptic curve cryptography. Finally, an Ethereum address is generated by taking the last 20 bytes of the Keccak-256 hash of the public key.

Question 2

In solidity, the outcome of dividing number -5 by integer 2 is

Accepted Answer

-2 due to the truncated decimal (rounded to zero)

Answer

In Solidity, integer division truncates any decimal part, effectively rounding the result towards zero. Therefore, when dividing -5 by 2, the mathematical result is -2.5, but Solidity's integer division truncates this to -2. This behavior is standard for integer arithmetic in many programming languages.

Question 3

What does it mean when we say, "A Hashing Algorithm is deterministic"?

Accepted Answer

When given the same input, it always generates the same output.

Answer

A deterministic hashing algorithm is one that consistently produces the exact same output hash whenever it is given the identical input. This property is fundamental to blockchain technology, as it ensures that data integrity can be reliably verified and that all network participants can independently and consistently arrive at the same hash for a given piece of data.

Question 4

What functions do private keys represent?

Accepted Answer

To verify signatures on documents and determine an address from.

Answer

Private keys serve critical functions in Ethereum's security model. They are used to cryptographically sign transactions, proving ownership of an address and authorizing fund transfers or contract interactions without revealing the private key itself. Additionally, an Ethereum address is deterministically derived from its corresponding public key, which in turn is generated from the private key.

Question 5

What does a transaction's nonce-field imply?

Accepted Answer

To defend off replay attacks

Answer

The `nonce` field in an Ethereum transaction is a sequential counter that tracks the number of transactions sent from a specific address. Its primary purpose is to prevent 'replay attacks,' where a malicious actor might attempt to re-broadcast an old, valid transaction. By requiring each transaction to have a unique, incrementing nonce, the network ensures that every transaction is processed only once.

Ethereum Developer Practice Test

Ethereum Developer Practice Test

Ethereum Developer Test 1