Blockchain Flashcards

Flashcards for reviewing key concepts from a blockchain lecture.

Blockchain (as a data structure)

data put together into units called blocks, connected like a chain

Blockchain (as an algorithm or protocol)

sequence of operations that cause the flow of many blockchain data structures

Blockchain (as a suite of technologies)

a combination of the data structure and algorithm that achieves consistency, trust and integrity of data

What is blockchain suitable for?

To reliably and irrefutably demonstrate that an action has been performed.

According to the notes, what are examples of objects of ownership?

money, car, house, kids, age, personal data etc.

Centralized institutions provide ownership guarantees, stemming from what?

institutions that bestow public trust

According to the notes, who do we believe can guarantee certainty, impartiality and honesty of entries in the register?

Government

What is a central idea of 'Wisdom of the Crowd'?

Decisions taken by a large group are always better than decisions made by small numbers of experts.

List the Properties of the Perfect Register discussed in the notes.

Openness, Irrevocableness, Nonforgeabilness, Veracitiness, Independentness, Watchfulness, Operationness, Persistenceness, Timeliness

According to the lecture notes, what is the dual nature of the perfect register?

Proof of ownership requires transparency, ownership manipulation requires privacy

To make blockchain operationess independently on politics, governments, institutions or dictators, what is the key feature?

Need for dispersion

Among advantages of a multicomponent system over single one, what can you list?

Higher computing power, ability to scale naturally, potentially higher reliability, possibly cost reduction.

What is a decentralized system?

A system whose components form a network without having any central element of coordination or control.

What are the major advantages of decentralized systems over centralized systems?

The functioning of the whole system does not depend on the condition of the central element, does not strictly depend on the condition of the network connecting its components.

What are the disadvantages of decentralized systems compared to centralized systems?

High communication and coordination overhead, Higher complexity in terms of algorithms, protocols and coding which may reflect overall system security.

Peer-to-peer systems consist of what?

individual, independent components (nodes) of equal rights and roles.

To be able to complete steps to decide about ownership, what tools are required?

Identification, Authentication, and Authorization.

What does Identification mean?

claiming to be someone or something.

What does Authentication mean?

proving that object really is what someone claim to be.

What does Authorization mean?

getting an access to something due to the previously authenticated identity.

How can you solve the problem of having a perfect ledger as the single source of truth?

Use a purely distributed peer-to-peer system of many ledgers to minimize chances of forged IT.

What is integrity in the context of blockchain?

ability to make true statements about ownership

Distributivity allows you to get what?

Robustness and independence on any centralization attempts.

Cryptography allows you to do what?

Preserve integrity of data and their invariance.

In our everyday life, save characters and keep them in unchanged form means what?

Printing data

Fingerprints are known as what type of relation?

Fingerprints are one-way relation.

What are desirable property every fingerprint should have?

Can be compute it quickly, It is deterministic, size of fingerprint can be fixed, You cannot recreate or guess contents of string based on fingerprint.

What are the two very important properties that should be fulfilled for a better way for calculating fingerprint?

Pseudorandom and Collision Resistant.

What is known as avalanche effect name?

Even the smallest change in input yield a fingerprint so different that the new fingerprint appears uncorrelated with the old (previous) fingerprint

What is Pre-image resistance?

Given a hash value h, it should be difficult to find any message m such that: h = hash(m)

What is Second pre-image resistance?

Given an input m1 it should be difficult to find a different input m2 such that: hash(m1) = hash(m2)

What is Collision resistance?

It should be difficult to find two different messages m1 and m2 such that: hash(m1) = hash(m2).

If Alice wants to send a message and be sure that no byte would be changed, what procedure can be followed?

Alice creates a combined sequence C concatenating the message M with the secret S appended to the end of the message: C = M + S, Calculate a hash Ha of C: Ha = hash(C) = hash(M + S)

What is a hash puzzle?

Find the nonce that combined with data yields a hash value meeting your requirements

What is mining?

This is an example of Proof of Work (PoW), the process of searching for a nonce.

When your data is constantly changing, what types of hashing can you distinguish?

Repeated, Independent, Combined, Sequential, Hierarchical

What is Hierarchical hashing?

This is the creation of one single hash value for a collection of data with a tree-like hierarchy of hash values with a single value on its top

the question is: How to thwart such a pre-computed dictionary attacks?

Make pre-computed dictionary useless

Hashes and hashing is used in the blockchain for what?

Computing a digital fingerprint of data; storing data in the way allowing an easy identification of any kind of change, guaranteeing its integrity; defining computational cost of new block of data.

In cryptography a play text is a text which you can read without any problems, a text without any what?

Transformation, changes and obscure procedures.

Plain text is also is the sequence of bytes called what?

A text you write on a paper with a pen, on a computer with a keyboard or any other classical way.

What is encrypted data or cypher text.

data after applying to it encryption procedure

In modern cryptography, what do you need to get plain text.

The (cryptographic) key.

In Symmetric cryptography how the key is used.

Identical key is used to do both the encrypting and decrypting of data

In Asymmetric cryptography how the key is used.

You always use two different keys, we say two complementary keys

From the asymmetric cryptography definition, what can you do if you only have one of the keys?

You create cypher text by applying your key to plain text, decrypt cypher text by applying your key to encrypted data that was created with the corresponding complementary key

Name these two keys specific names give to highlight public-private roles,

typically these keys are called the private key and public key. For that reason, asymmetric cryptography is called public-private-key cryptography

There are two general ways you can use the pair of keys, what are they?

public to private mode, private to public mode.

The blockchain uses asymmetric cryptography in order to achieve what two goals

identify accounts, authorize transactions.

How does Blockchain uses asymmetric cryptography?

Identify accounts; authorize transactions.

A digital signature must have the same characteristics as a traditional signature has, what are they?

Can be easily done by its owner, is hard to falsify, inseparable from signed document.

What are digital signatures used to prove?

Authenticity, Integrity, Non-repudiation

Each block consists of what two major data structure?

block header, data structure

What does block header contain?

Is identified by its cryptographic hash value, contains a hash reference to its preceding block header, and contains a hash reference to the application-specific data.

The very first block is sometimes called?

genesis block

The field previousBlockHash must be set to what?

a hash of previous block

In calculating had of a block what fields should already be set during the time when block was created?

Timestamp, DataMainHash

When hash calculation of the block is done, what values you need to add to data header structure?

blockHash with value equal to h, mineTime with value equal to the total time you need to find correct nonce.

The idea of how blockchain makes its data safe by ensuring its immutability is quite simple. You should design a system in which you have to somehow pay for placing your data in it, by what?

solving hash puzzle

What must you do to minimize attempt to manipulate or forge the history of transaction

design it as a purely distributed peer-to-peer system, open to everyone.

In the Bitcoin, how long will it take you to generate a block?

Limited by difficulty to one block every 10 minutes in average.

What makes no identical to candidate to blocks to be built?

the first transaction in every block is unique to the node trying to mine that block.

A nonce

number used once is called What?

Why extraNonce is required?

To be able to find a valid nonce.

The miners have found a solution which wasn't designed for a particular case but become the standard which is what?

by adjusting what's referred to as an extra nonce

You may find interesting that Bitcoin mining proof of work is based on what proof of work algorithm?

Hacheash

The blockchain heavily depends on hashes, what is used for what?

computing a digital fingerprint of data, storing data in the way allowing an easy identification, defining computational cost of new block of data

What is the target is supposed to do.

ensure that blocks are mined once every 10 minutes on average

What does difficulty do?

controls the target

Why you should change difficulty frequently?

to make it sure that blocks with data are added to the blockchain at close to regular intervals, regardless of the general condition of the system.

What is (total) blockchain, the chain mean said different word?

the chainwork,the weight, is the sum of chainwork of all present blocks.

What are the core features underlying governance of blockchain system?

Validation rules, reward rules, punishment rules, control rules, competition rules

Who the Blockchain punishment is addressed to?

for people with bad intentions but rather for people hoping for easy money and adds a block with insufficient care which later turns out to be identified as invalid or useless.

Why a message to switch to a new block

The message that received a new block to. To switch between the two phases in is not exactly identical in to some external factor

At any given point in time, all nodes of the system are in either of the two states, what are those two state?

Try to be the next node that creates a new block, evaluate a new block that was created and submitted by one of the node.

The time is the essence of which of the following??

Consequences of message passing imperfections

if there are two chains and one of them is longer, what's the rule that nodes are expected to adopt as that one being more reliable (Correct)?

That must be correct, because none would invest into forging historic block and developing invalid chain

In consequence some blocks are going to require more or less energy to mine than others and the chain that required the most energy has not been changed for a known?

Because you are random

Fork on the block chin is seen as which situation?

A fork is simply an occurrence of the disagreement about the sequence of blocks either their other or their presence or absence

For the most of the time it is equitant to the chain with the most blocks in it , but to be more precise it is always the chain with the most amount of word in what?

chainwork