Blockchain Technology Cryptography in Blockchain 4

Question 1

What is a commitment scheme in cryptography, and how is it used in blockchain protocols?

Accepted Answer

A method to bind a value secretly, then reveal it later without being able to change it

Answer

A commitment scheme allows a party to commit to a value (hiding it) and later open (reveal) it, with the guarantee it cannot be altered after committing.

Question 2

Which attack does the 'avalanche effect' in hash functions help defend against?

Accepted Answer

Differential cryptanalysis and pattern detection

Answer

The avalanche effect ensures a single-bit change in input causes roughly half the output bits to flip, making differential analysis impractical.

Question 3

In SNARKs (Succinct Non-interactive Arguments of Knowledge), what is the 'trusted setup' and why is it controversial?

Accepted Answer

A one-time parameter generation where secret 'toxic waste' must be destroyed to ensure soundness

Answer

The trusted setup generates public parameters; if the secret randomness ('toxic waste') is not destroyed, it could allow forging false proofs.

Question 4

Which of the following describes a 'birthday attack' against a hash function?

Accepted Answer

Finding two arbitrary inputs that collide by exploiting the birthday paradox's probability threshold

Answer

The birthday paradox shows that collisions become likely after approximately √(2^n) attempts for an n-bit hash, far fewer than brute-forcing a specific pre-image.

Question 5

What is a Pedersen commitment and how does it differ from a simple hash commitment?

Accepted Answer

A Pedersen commitment is homomorphic, allowing mathematical operations on committed values without revealing them

Answer

Pedersen commitments are additively homomorphic, meaning commitments to values can be added together in a way that corresponds to adding the underlying values.

Blockchain Practice Test

Blockchain Practice Test

Blockchain Technology Cryptography in Blockchain 4