Introduction to Bitcoin and Blockchain

Questions and Answers

What is Bitcoin?

A type of traditional currency

Decentralized digital currency (correct)

A credit card payment system

A government-issued currency

What does a Bitcoin transaction involve?

Signing a statement that transfers ownership from one Bitcoin address to another.

What is Blockchain?

A sequence of transactions that all nodes must agree on.

What is Bitcoin mining?

The processing of transactions where blocks of current transactions are added to the blockchain. Signup and view all the answers

What is the role of blocks in the blockchain?

They contain sequences, timestamps, and hashes. Signup and view all the answers

What occurs during the Bitcoin consensus process?

Transactions are broadcast, and valid blocks are accepted by other nodes. Signup and view all the answers

Anyone can mine new blocks for the blockchain.

True Signup and view all the answers

What is proof-of-work?

A mechanism that requires computing a puzzle that is hard to solve but easy to validate. Signup and view all the answers

What is a hard fork?

When one cryptocurrency splits into two, leading to different versions of transaction history. Signup and view all the answers

What is the Dark Web?

A part of the web that is inaccessible through standard browsing. Signup and view all the answers

What is symmetric encryption?

Using the same key to encode and decode messages. Signup and view all the answers

What is asymmetric encryption?

A method using pairs of keys for encryption and decryption. Signup and view all the answers

What does TLS/SSL provide?

Encryption of content that goes into TCP payload. Signup and view all the answers

What does HTTPS example: key exchange involve?

Client generates a random key, encrypts it with the server's public key. Signup and view all the answers

What is packet switching?

A method where packets are sent by hosts through the internet. Signup and view all the answers

What does the OS do?

Create abstractions to make hardware easier to use, manage shared hardware resources. Signup and view all the answers

Which of these are components of OS abstractions? (Select all that apply)

File system Signup and view all the answers

Which of these are components of hardware? (Select all that apply)

CPU Signup and view all the answers

What is the process abstraction?

An OS abstraction for execution, consisting of address space, one or more threads, and other resources. Signup and view all the answers

What are the components of a process?

Named with a unique process ID (PID), contains all the state for the program in execution, and one or more threads. Signup and view all the answers

What do threads share?

Heap memory allocated by the executing program Signup and view all the answers

What is a thread?

An active object that describes the execution of a program. Signup and view all the answers

When are threads useful?

When multiple tasks occur simultaneously, especially with slow resources like network servers. Signup and view all the answers

What happens in web servers with threads?

Each thread handles a request and is blocked on I/O while others can run. Signup and view all the answers

When should you use processes instead of threads?

When you want separate address space Signup and view all the answers

What are atomic operations?

Operations that are indivisible and occur in their entirety or not at all. Signup and view all the answers

What is the purpose of locks in threading?

To avoid overwrites by controlling access to shared resources. Signup and view all the answers

What is a network socket?

A virtual NIC for a process that allows for bidirectional communication. Signup and view all the answers

What are cloud services primarily concerned with?

Infrastructure as a Service (IaaS), Software as a Service (SaaS), and Platform as a Service (PaaS). Signup and view all the answers

What is AWS's Elastic Compute Cloud (EC2)?

A service that offers machines for rent to users. Signup and view all the answers

What is the concept of virtualization?

Cutting a large machine into smaller virtual machines. Signup and view all the answers

What is Boolean retrieval?

True or false exact match retrieval that often yields poor results. Signup and view all the answers

What does TF x IDF represent?

Term frequency times inverse document frequency, used for evaluating the importance of a word in a document relative to a collection. Signup and view all the answers

What is MapReduce?

A programming model for processing large data sets with a master, mappers, groupers, and reducers. Signup and view all the answers

What are the main functions of a central bank?

Lending money to other banks and controlling the supply of money in the economy. Signup and view all the answers

What is round robin DNS?

Multiple IP addresses for a single domain name, responding with a permuted list of addresses. Signup and view all the answers

What does load balancing do?

Acts as a middleman between client and DNS, forwarding requests to backend servers. Signup and view all the answers

What is Jaccard Similarity Coefficient?

A measure of similarity between two sets that indicates how closely they intersect. Signup and view all the answers

Study Notes

Operating System Fundamentals

OS creates abstractions to simplify hardware usage and manages shared resources.
Key abstractions of the OS include Process, File System, Virtual Memory, and Sockets.

Hardware Components

Essential hardware components are CPU, Disk, RAM, and Network.

Process Abstraction

Represents a program in execution, containing address space, threads, and resources like file handles.
Each process is identified by a unique Process ID (PID) and maintains execution state.

Threads and Their Functionality

Threads are active entities of execution sharing code and resources such as heap memory and global variables.
Each thread has a private execution stack and registers to maintain its state.
Multithreading is useful for achieving parallelism during resource-intensive tasks, e.g., network servers.

Communication via Sockets

Sockets enable network communication, with TCP providing reliable connections while UDP sends unordered packets.
A typical socket connection involves BINDing, LISTENing, and accepting requests.

Cloud Services and Virtualization

Key cloud service models include IaaS, SaaS, and PaaS.
AWS services like EC2 and S3 provide virtual computing and storage solutions through virtualization techniques.

Search Engine Models

Boolean retrieval provides simplistic true/false output but is ineffective.
The term-document incidence table maps terms to documents for efficient querying.

Document Representation and Indexing

Documents can be viewed as vectors, measuring term frequency for similarity assessment.
TF-IDF (Term Frequency-Inverse Document Frequency) scores help weigh document relevance based on common and rare terms.

Evaluation Metrics

Precision measures relevant documents retrieved, while Recall indicates relevant documents identified out of total available.
Kendall's tau and Mean Reciprocal Rank provide rank correlation and position of first correct answers, respectively.

PageRank Algorithm

PageRank operates on a directed graph of web pages. Pages receive scores based on links from important pages.
Sink nodes may gather rank without outgoing links, requiring methods to prevent rank drain.

Crawling and Indexing Strategies

Web crawlers index all static pages, while dynamic pages depend on server-side links.
Inverted indexes allow quick access by mapping terms to associated documents.

Data Management Techniques

Deduplication ensures document uniqueness through methods like shingling and the Jaccard similarity coefficient.
MapReduce framework enables efficient large-scale data processing by breaking tasks into mappable and reducible components.

Bitcoin and Digital Currency

Bitcoin operates as a decentralized digital currency based on blockchain technology and requires cryptographic security for transactions.
Transactions involve public and private keys, maintaining ownership without a central authority.

Blockchain Characteristics

A blockchain is a sequential, tamper-proof transaction record built from blocks containing metadata and transaction data, guaranteeing the integrity of digital currencies like Bitcoin.### Bitcoin Consensus
Transactions are disseminated to all network nodes, where a random node signs a block containing new transactions and the hash of the previous block.
If transactions are valid, other nodes accept the new block; invalid transactions are ignored.
The process is repeated for subsequent blocks, with the longest chain deemed canonical.
A valid canonical chain requires an "honest majority" to prevent manipulation.

Mining the Blockchain

Anyone can mine blocks for the blockchain, but mining is necessary as a block's validity relies on its hash being below a target value.
The hashing process requires significant time and computational effort.

Proof-of-Work

Proof-of-work puzzles are designed to be difficult to compute but easy to validate.
A solution to this puzzle serves as proof of spent computational effort.
The target difficulty can be adjusted to calibrate mining speed, aiming for an average of 10 minutes per block.

Blockchain Forks

Concurrent discovery of a new block by two miners can lead to a fork.
The fork that grows quicker, due to more computational power, is considered valid.
A fork can result in a new cryptocurrency, differentiating transaction histories and ownership versions.

Bitcoin Miners' Motivation

Miners, as block creators, can reward themselves with bitcoins from transaction inclusions.
This process is fundamental for both earning bitcoins and increasing the total supply of the cryptocurrency.

Bitcoin Reward Function

The reward for mining bitcoins halves approximately every four years to control inflation.

Bitcoin Creation Difficulty Adjustment

The complexity of creating a nonce for blocks increases over time, making mining progressively more challenging.

Hard Fork

A hard fork creates two distinct cryptocurrencies from one, sharing a partial transaction history.
Holders of the original asset will possess both new assets, often resulting in higher combined market values.
All nodes must upgrade their software for the hard fork to take effect.

The Dark Web

The dark web is a concealed part of the internet, accessible only through specific anonymous networks.
It is enveloped by the deeper segment of the internet known as the deep web.

Packet Switching

The internet operates on a best-effort, packet-switched model with packets being the fundamental unit of data transmission.
Packets may experience delays or failures in transit, with IP routers central to internet functioning.

Internet Protocol (IP)

IP operates in a connectionless manner, utilizing a "store and forward" mechanism.
Different packets can take diverse paths to reach the same destination.
Accurate destination information is crucial; otherwise, packets cannot be delivered.

Desirable Properties of Communication

Essential properties include confidentiality, sender authenticity, message integrity, freshness, and anonymity.

Symmetric Encryption

Utilizes the same key for both encoding and decoding messages, ensuring fast computation.
Provides confidentiality by preventing unauthorized understanding of the message.

Asymmetric Encryption

Involves a pair of keys: public and private.
One key encrypts the message while the other decrypts it, with the keys being mathematically independent.

Public Key Infrastructure

Certificate authorities (CAs) are responsible for verifying identities and public keys.
Public keys for major CAs are integrated into web browsers.

TLS/SSL - Transport Layer Security/Secure Sockets Layer

Indicated by "https://", this protocol encrypts all content in the TCP payload to ensure secure communication.

HTTPS Example: Certificate Exchange

The server verifies its identity to the client by sending an SSL certificate and its public key.
The client checks the certificate against a list of trusted CAs to confirm the server's legitimacy.

HTTPS Example: Key Exchange

The client generates a random key for future symmetric encryption and encrypts it using the server's public key.
Later, traffic is secured using symmetric encryption with the agreed shared key.

Packet Inspection

Each network packet contains source and destination IP addresses, with source addresses potentially being spoofed.
The packet's source and destination information is observable by any entity monitoring the network.

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Description

This quiz covers fundamental concepts related to Bitcoin and blockchain technology. Explore key topics such as Bitcoin transactions, mining processes, and the role of consensus in the blockchain system. Perfect for beginners looking to deepen their understanding of cryptocurrencies.