Cryptographic Principles in Blockchain Flashcards

Which cryptographic principle is primarily responsible for ensuring the integrity and immutability of data within a blockchain by creating a unique, fixed-size output from variable-sized transaction data?

Answer: Hashing

Hashing is a one-way cryptographic function that takes an input of any size and produces a fixed-size string of characters, known as a hash. In blockchain, any small change to the input data (like a transaction detail) will result in a completely different hash. This property makes it easy to detect tampering and ensures the integrity of the data stored in each block, linking them together in a secure chain.

A user wants to authorize a cryptocurrency transaction on a blockchain network. Which of the following cryptographic tools allows the user to prove ownership of the funds and authorize the transfer without revealing their secret key?

Answer: Digital Signature

A digital signature is created using the sender's private key and the transaction data. Others on the network can then use the sender's public key to verify that the signature is authentic and that the transaction has not been altered, thus proving ownership and authorizing the transaction without exposing the private key.

In the context of a Bitcoin block, what is the primary purpose of a Merkle Tree?

Answer: To efficiently and securely verify the integrity of a large set of transactions.

A Merkle Tree, or hash tree, summarizes all the transactions in a block by repeatedly hashing pairs of transaction hashes until a single hash, the Merkle Root, is left. This structure allows for efficient verification of transactions; a user can check if a transaction is included in a block by only needing the Merkle Root and a small number of hashes (the Merkle proof), rather than downloading and checking every single transaction.

Elliptic Curve Cryptography (ECC) is widely used in blockchains like Bitcoin and Ethereum. What is its primary advantage over older algorithms like RSA?

Answer: It provides the same level of security with smaller key sizes.

The main advantage of Elliptic Curve Cryptography (ECC) is that it can provide the same level of security as algorithms like RSA but with significantly smaller key sizes. This leads to lower computational overhead, faster operations, and reduced storage and bandwidth requirements, which are crucial for the efficiency and scalability of a blockchain network.

A developer is building a new blockchain protocol and needs to select a hashing algorithm. Which of the following is a critical property for the chosen algorithm to prevent attackers from finding two different inputs that produce the same hash output?

Answer: Collision resistance

Collision resistance is a crucial property of a cryptographic hash function, meaning it should be computationally infeasible to find two different inputs that produce the exact same hash output. If a hash function is not collision-resistant, an attacker could create a fraudulent transaction that has the same hash as a legitimate one, compromising the integrity of the blockchain.

In a public-key cryptography system as used in blockchain, what is the relationship between the private key and the public key?

Answer: The public key is mathematically derived from the private key, but it is computationally infeasible to reverse the process.

In asymmetric cryptography (public-key cryptography), the public key is generated from the private key through a one-way mathematical function, typically using elliptic curve multiplication in blockchains. While it is easy to generate the public key from the private key, it is computationally infeasible to derive the private key from the public key, which is fundamental to the security of the system.