Fundamental Cryptography Concepts Flashcards
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Read the first 7 Fundamental Cryptography Concepts flashcards as text
What is a 'key derivation function' (KDF) and how is it used in Bitcoin wallets?
Answer: A KDF derives cryptographic keys from a passphrase or seed using controlled computational difficulty to resist brute-force
KDFs like PBKDF2 add computational cost (iterations) to slow down attackers trying to brute-force a password into a wallet key.
In Bitcoin's HD wallet standard (BIP32), what does 'hardened derivation' protect against?
Answer: If a child private key is leaked, hardened derivation prevents attackers from deriving the parent private key
Hardened child keys use the parent private key as input, so a compromised child private key cannot be used to reverse-engineer the parent or sibling keys.
What is the role of a 'checksum' in Bitcoin address encoding?
Answer: It adds error-detection bytes to the address so typos or corrupted characters are caught before sending funds
Bitcoin Base58Check encoding appends 4 checksum bytes (first 4 bytes of double-SHA256) to detect transcription errors before a transaction is broadcast.
Which of the following correctly describes how Bitcoin uses 'public key cryptography' for transaction authorization?
Answer: The sender signs the transaction with their private key; any node can verify the signature using the sender's public key
Bitcoin uses ECDSA where the spender's private key produces a signature and any verifier can use the corresponding public key to confirm authenticity.
What does 'computational infeasibility' mean in the context of Bitcoin cryptographic security?
Answer: Breaking the cryptography would require more computing resources or time than is practically available, even with current hardware
Computational infeasibility means the attack would take longer than the age of the universe or require more energy than exists, making it practically impossible.
How does HMAC (Hash-based Message Authentication Code) differ from a standard cryptographic hash?
Answer: HMAC incorporates a secret key into the hashing process, providing both integrity and authentication
HMAC combines a secret key with the message before hashing, so only parties with the key can produce or verify the MAC, adding authentication to integrity.
In the context of BIP39 mnemonic seed phrases, what cryptographic function converts the word list into a binary seed?
Answer: PBKDF2 with HMAC-SHA512, applying 2048 iterations to stretch the mnemonic into a 512-bit seed
BIP39 uses PBKDF2-HMAC-SHA512 with 2048 iterations and an optional passphrase salt to derive the 512-bit master seed from the mnemonic.