Blockchain Week 2
What is Script?
A stack-based language No loops
What is a Bitcoin Transaction?
Allows for a transfer of bitcoins between accounts
What are 6 attributes of Bitcoin Transactions?
ID Inputs Fee amount Size Outputs Total amount transferred
What is Script not?
It is not Turing complete, meaning that there is no halting problem
When was the first open-source code for Bitcoin released?
January 2009
What are the transaction types?
One-To-One One-to-Many Many-to-one (consolidation?) Many-to-Many (joint payment?)
What is unique about P2PKH?
Original address Starts with 1
What scripts do we have for Bitcoin addresses?
P2PKH (Pay to PUbKeyHash) P2SH (Pay to Script Hash) Bech32 (Segwit Address)
If you wanted to make a transaction from several different people what script should you use?
P2SH
What is Bitcoin?
A currency: BTC token A payment method A ledger
What is Bitcoin?
A block-chain based electronic cash system (cryptocurrency)
How many instructions does Bitcoin Script have?
256
What is a Bitcoin address?
A 26-34 alphanumeric Base-58 string.
What do Wallets do?
Calculate the users' balances by scanning the ledger and aggregating all UTXOs owned by the user
What do Bitcoin Accounts do?
Create a secret and public key pair
What does Script support?
Cryptographic operations 1. Secure hashing 2. Signature verificaction 3. Multi-signature verification
What does the merkelRootHash do in the BC?
Has all of the transactions in the tree (allows you to see if the transaction exists in a block, proves membership)
Why do we use Base-58?
Don't want 0OIl to happen A string with non-alphanumeric characters is not as easily accepted as an account number E-mail usually won't linebreak if there's no punctuation Double clicking selects who string
What are the different ways to obtain BTC?
Exchange fiat money (Coinbase, Kraken, Shapeshift) Bitcoin ATMS Someone transfers BTC to your address Through mining
How do you get the address of an account?
H160(public key)
What are some attributes of Bitcoin?
Maintained by a peer-to-peer network The network maintans a decentralized ledger of transactions Double-spending is prevented
What are some commonly used instructions in Script?
OP_DUP OP_HASH160 OP_EQUALVERIFY OP_CHECKSIG OP_CHECKMULTISIG
What is a coinbase transaction?
Purpose is to create new bitcoins One transaction per block Does not have inputs (does not reference UTXOs)
What is a regular transaction?
Purpose: transfer bitcoints The majority of transactions in Bitcoin
What hash functions are used to generate Bitcoin addresses?
RIPEMD-160 and SHA-256 RIPEMD160(SHA256(public key))
What is the smallest unit of Bitcoin?
Satoshi = 1e-8 Bitcoin
Who invented Bitcoin?
Satoshi Nakamoto
What is unique to P2SH?
Starts with 3 Allows for complex transactions (e.g. MultiSig accounts)
What is unique to Bech32?
Supports segregated witness (bigger block size) Starts with bc1
What does the Bitcoin ledger not store?
The balance of each account, instead it tracks UTXos intransactions
What is lock time?
The earliest time at which the transaction can be added to the blockchain
What is the hash of a transaction?
The hash of the whole transaction
What are inputs to a Bitcoin Transaction?
The hash pointer to a UTXO n - which output to grab (can be multiple) ScriptSig -the signature script to claim the above output
What is UTXO?
Unspent transaction output Amount left after executing a transaction (indivisible) sum of bitcoins locked to an address on the blockchain
What is the nonce in a BC?
What you can change to get the right hash that will fit in the chain
What does every transaction have?
a transaction fee
What are the outputs of a Bitcoin Transaction?
value - how many BTCs ScriptPubKey - script that locks an output to a public key (also contains script instructions)