CBCP Cryptography and Security 4 — Questions and Answers
Question 1: What is the Schnorr signature scheme's key advantage over ECDSA in blockchain contexts?
- It uses larger key sizes for greater security
- It natively supports signature aggregation, allowing multiple signatures to be combined into one (Correct answer)
- It is quantum-resistant by design
- It eliminates the need for hashing
Correct answer: It natively supports signature aggregation, allowing multiple signatures to be combined into one
Schnorr signatures support linear aggregation (e.g., MuSig), enabling multiple signers to produce a single compact signature, improving scalability and privacy.
Question 2: In symmetric encryption used for blockchain data at rest, what is the fundamental limitation compared to asymmetric encryption?
- It is too slow for bulk encryption
- It requires a secure channel to share the secret key between parties (Correct answer)
- It cannot authenticate the sender
- It does not support key lengths above 128 bits
Correct answer: It requires a secure channel to share the secret key between parties
Symmetric encryption requires both parties to already share a secret key, making initial key exchange the central security challenge.
Question 3: What is a Pedersen commitment, and where is it commonly used in blockchain privacy?
- A hash-based commitment used in Bitcoin scripting
- A homomorphic commitment scheme allowing arithmetic on hidden values, used in confidential transactions (Correct answer)
- A time-locked commitment for payment channels
- An RSA-based commitment for identity verification
Correct answer: A homomorphic commitment scheme allowing arithmetic on hidden values, used in confidential transactions
Pedersen commitments are computationally hiding and perfectly binding; their homomorphic property allows verifying transaction balance without revealing amounts, as in Confidential Transactions.
Question 4: What does 'perfect forward secrecy' (PFS) mean in the context of blockchain node communications?
- Past session keys cannot be compromised even if the long-term private key is later revealed (Correct answer)
- All nodes must share the same encryption key for forward compatibility
- Transactions are irreversible once confirmed
- Block headers are encrypted with ephemeral keys that never expire
Correct answer: Past session keys cannot be compromised even if the long-term private key is later revealed
PFS ensures that session keys derived from ephemeral key exchanges remain secure even if the server's long-term private key is later compromised.
Question 5: How does a ring signature in Monero provide sender anonymity?
- It encrypts the sender's address using AES-256
- It allows a signer to sign on behalf of a group without revealing which group member actually signed (Correct answer)
- It replaces the sender's address with a stealth address shared with all nodes
- It uses zero-knowledge proofs to hide the transaction graph entirely
Correct answer: It allows a signer to sign on behalf of a group without revealing which group member actually signed
Ring signatures let one member of a group (ring) sign a message such that any ring member could plausibly be the signer, providing sender ambiguity.
Question 6: What is the difference between a hot wallet and a cold wallet from a cryptographic security standpoint?
- Hot wallets use RSA; cold wallets use ECC
- Hot wallets keep private keys connected to the internet; cold wallets keep keys fully offline (Correct answer)
- Cold wallets encrypt keys with AES; hot wallets use no encryption
- Hot wallets use multisig; cold wallets use single-key schemes
Correct answer: Hot wallets keep private keys connected to the internet; cold wallets keep keys fully offline
The key distinction is internet exposure: hot wallets have keys accessible online (higher convenience, higher risk), while cold wallets keep keys air-gapped offline.
Question 7: What cryptographic primitive underlies atomic swaps between different blockchains?
- Ring signatures
- Hash Time-Locked Contracts (HTLCs) using SHA-256 preimage secrets (Correct answer)
- Threshold signatures with a trusted third party
- Pedersen commitments with Bulletproofs
Correct answer: Hash Time-Locked Contracts (HTLCs) using SHA-256 preimage secrets
Atomic swaps use HTLCs where funds are locked with a hash and can only be claimed by revealing the preimage within a time window, enabling trustless cross-chain exchange.
CBCP Cryptography and Security 4
What is the Schnorr signature scheme's key advantage over ECDSA in blockchain contexts?