Melanie Rieback, Klaus Kursawe - Blockchain Security: Melting the "Silver Bul...Codemotion
The document summarizes some of the security issues with blockchain technology. It discusses how blockchain is not a "silver bullet" and does not inherently solve problems like privacy and security of smart devices. It outlines various application security issues with complex code, protocols, and difficulty of updates on blockchains. Concerns over data immutability and security of smart contracts are also covered. The document questions whether blockchain truly provides the level of decentralization and anonymity claimed, and outlines some impossibility results and limitations of existing approaches to achieving security and privacy in blockchain systems.
A brief introduction to Blockchain and the underlying technology of distributed computing, challenges and future scope.
Copyrights belong to the respective owners, intention is purely for informational/educational purpose
I would like to thank various blogs, technical tutorials, books, videos to help me understand the basics and collate this presentaion
An Introduction to Blockchain, Bitcoin, and CryptoEconomics.Kris Bruynson
This document provides an introduction to blockchain, bitcoin, and cryptocurrencies. It begins by explaining what blockchain is and how it works as a distributed ledger using a peer-to-peer network. It then discusses how blockchain verifies and adds transactions through mining and reaches consensus. The document notes both benefits and limitations of blockchain, and discusses how cryptocurrencies derive value from speculation and monetary theory rather than equity. It concludes by acknowledging both the hype and promise of blockchain technology.
Introduction to Blockchain Web3 SessionDSCIITPatna
Blockchain technology has been around since 2008 with the introduction of Bitcoin. It utilizes a decentralized digital ledger called a blockchain, which consists of records called blocks that are linked together in a growing list. Each block contains transaction data as well as a reference to the previous block. This allows transactions to be recorded in a verified and permanent way without the need for a central authority. There are various components that make up a blockchain network including nodes that host copies of the blockchain and wallets that store private and public keys for sending and receiving cryptocurrency. Various consensus mechanisms like proof-of-work and proof-of-stake are used to verify transactions and reach agreement across the decentralized network. Blockchain technology provides advantages like reduced costs and increased
The document provides an agenda for a presentation on blockchain technology and its applications in the energy industry. The presentation will cover fundamentals of blockchain like digital wallets and transactions, how blockchains work through mining and consensus mechanisms, and introduce smart contracts on the Ethereum network. It will also discuss how blockchain can help modernize the electricity grid and provide an ecosystem of players and platforms in the energy sector, highlighting challenges and benefits of implementing blockchain technology.
After an explosion of altcoins and funding, technical constraints and regulatory angst have taken over the headlines. Still, the frenzy of the past two years set the stage for the next wave of adoption with a steady inflow of talent and new, uniquely compelling use cases of digital assets.
Blockchains are distributed ledgers that use consensus protocols to track ownership or transactions across copies of the ledger maintained by members. A blockchain uses a consensus protocol like proof-of-work to agree on changes and additions to the distributed ledger. Membership in blockchains can be open to anyone, like in Bitcoin, or restricted to a fixed group. While blockchains provide advantages like distributed trust, achieving scalability is challenging due to the need for consensus among all members on every change.
Blockchain overview, use cases, implementations and challengesSébastien Tandel
Most know about Bitcoin, the well-known crypto-currency. Less know the details about the underlying and enabling technology, Blockchain.
Hopefully, this presentation provides enough insights to understand blockchain concepts and why it's perceived to potentially disrupt many market segments, from retail to governments, from finance to health care. At last, I hope to brush fairly the many challenges of this rather new technology.
Melanie Rieback, Klaus Kursawe - Blockchain Security: Melting the "Silver Bul...Codemotion
The document summarizes some of the security issues with blockchain technology. It discusses how blockchain is not a "silver bullet" and does not inherently solve problems like privacy and security of smart devices. It outlines various application security issues with complex code, protocols, and difficulty of updates on blockchains. Concerns over data immutability and security of smart contracts are also covered. The document questions whether blockchain truly provides the level of decentralization and anonymity claimed, and outlines some impossibility results and limitations of existing approaches to achieving security and privacy in blockchain systems.
A brief introduction to Blockchain and the underlying technology of distributed computing, challenges and future scope.
Copyrights belong to the respective owners, intention is purely for informational/educational purpose
I would like to thank various blogs, technical tutorials, books, videos to help me understand the basics and collate this presentaion
An Introduction to Blockchain, Bitcoin, and CryptoEconomics.Kris Bruynson
This document provides an introduction to blockchain, bitcoin, and cryptocurrencies. It begins by explaining what blockchain is and how it works as a distributed ledger using a peer-to-peer network. It then discusses how blockchain verifies and adds transactions through mining and reaches consensus. The document notes both benefits and limitations of blockchain, and discusses how cryptocurrencies derive value from speculation and monetary theory rather than equity. It concludes by acknowledging both the hype and promise of blockchain technology.
Introduction to Blockchain Web3 SessionDSCIITPatna
Blockchain technology has been around since 2008 with the introduction of Bitcoin. It utilizes a decentralized digital ledger called a blockchain, which consists of records called blocks that are linked together in a growing list. Each block contains transaction data as well as a reference to the previous block. This allows transactions to be recorded in a verified and permanent way without the need for a central authority. There are various components that make up a blockchain network including nodes that host copies of the blockchain and wallets that store private and public keys for sending and receiving cryptocurrency. Various consensus mechanisms like proof-of-work and proof-of-stake are used to verify transactions and reach agreement across the decentralized network. Blockchain technology provides advantages like reduced costs and increased
The document provides an agenda for a presentation on blockchain technology and its applications in the energy industry. The presentation will cover fundamentals of blockchain like digital wallets and transactions, how blockchains work through mining and consensus mechanisms, and introduce smart contracts on the Ethereum network. It will also discuss how blockchain can help modernize the electricity grid and provide an ecosystem of players and platforms in the energy sector, highlighting challenges and benefits of implementing blockchain technology.
After an explosion of altcoins and funding, technical constraints and regulatory angst have taken over the headlines. Still, the frenzy of the past two years set the stage for the next wave of adoption with a steady inflow of talent and new, uniquely compelling use cases of digital assets.
Blockchains are distributed ledgers that use consensus protocols to track ownership or transactions across copies of the ledger maintained by members. A blockchain uses a consensus protocol like proof-of-work to agree on changes and additions to the distributed ledger. Membership in blockchains can be open to anyone, like in Bitcoin, or restricted to a fixed group. While blockchains provide advantages like distributed trust, achieving scalability is challenging due to the need for consensus among all members on every change.
Blockchain overview, use cases, implementations and challengesSébastien Tandel
Most know about Bitcoin, the well-known crypto-currency. Less know the details about the underlying and enabling technology, Blockchain.
Hopefully, this presentation provides enough insights to understand blockchain concepts and why it's perceived to potentially disrupt many market segments, from retail to governments, from finance to health care. At last, I hope to brush fairly the many challenges of this rather new technology.
This document discusses developing a digital resource management application using blockchain. It begins with an introduction to the presenter and outlines topics to be covered including fundamentals of blockchain, use cases, and developing a healthcare resource management application using blockchain. Examples of blockchain applications developed by students are provided, such as claims processing on Hyperledger and using blockchain for invoice financing. The conclusion emphasizes that blockchain can be used to manage digital resources involving multiple untrusting parties through mechanisms like fine-grained access control.
Blockchain is a distributed ledger technology that allows for the safe distribution of a ledger across multiple nodes. It works by having each transaction digitally signed and added in a "block" along with a proof of work. This prevents double spending and allows nodes to reach consensus on the transaction history without a centralized authority. Smart contracts enable decentralized applications to run transactions automatically according to the program. However, first generation blockchains face challenges around centralization, scalability, and smart contract quality. New solutions aim to address these through alternative consensus methods, off-chain transactions, and designed smart contract languages.
The document discusses the Lightning Network and how it enables payments and transfer of small amounts of data. It describes how Lightning Network channels work and how payments can be routed across multiple channels. It then discusses an open-source solution called c13n that allows nodes to read and write data over Lightning Network payments in an efficient and secure manner. Finally, it outlines some potential use cases for sending data and payments over Lightning Network such as messaging apps, serverless computing, and decentralized oracles.
BlockChain basics for the non-technical banker covering what's happening, what the opportunities are, and the problems we all face. Covers BitCoin and Ethereum with brief mentions made of Ripple and the HyperLedger project.
Discussed about the Blockchain and how it works
Also the advantages of Blockchain over centralized system and some drawbacks are also mentioned.
Discussion on bitcoin and Cryptocurrency
Creating our own cryptocurrency for startups.
Snapshots are attached.
Rohan provided an overview of how cryptocurrency works including key terms like blockchain, mining, decentralization, and proof of work. Blockchain is a digital ledger that records transactions across a network of computers. Mining is the process of verifying transactions and adding them to the blockchain to introduce new coins as a reward. Decentralization means control is distributed across the network rather than centralized. Proof of work is the consensus algorithm where miners compete to complete transactions. Rohan also discussed advantages like transparency and security as well as challenges like energy use and implementation costs.
The document discusses the wormhole bridge attack that occurred in February 2022, where an attacker exploited a security flaw in the wormhole bridge to steal approximately $325 million worth of cryptocurrency. Wormhole is a bridge that allows transfer of digital assets between different blockchains. The attacker was able to forge a signature to mint a large amount of wrapped ether on the Solana blockchain. This left a deficit between the collateral held in wormhole. Transaction data shows the attacker has since moved some of the stolen funds between decentralized exchanges and stablecoins. The hack highlights risks of interacting with bridges and importance of thorough research for crypto projects.
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This is the presentation used at the May 15 Brisbane Bitcoin VS Bitcoin Cash Meetup.
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Note - it's a rush job, slapped together in a few hours so there are probably mistakes. In any case, I hope you find it informative.
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Blockchain is an open, distributed ledger that can record transactions between two parties efficiently and permanently. It works by linking transaction records into blocks secured by cryptography, forming a chain. Tampering with a block would change its hash and break the chain. Blockchains use consensus algorithms like proof-of-work and proof-of-stake to validate transactions without centralization. Smart contracts enable blockchain applications. Supply chain management may be a promising application area due to blockchain's decentralization, immutability, and transparency. Examples include partnerships between IBM/Walmart and Everledger for provenance tracking.
The document provides an overview of a blockchain conference agenda with the following key points:
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- It defines participants, transactions, and contracts on blockchains. Participants are members with identities and roles. Transactions are asset transfers between participants. Contracts set conditions for transactions.
- It explains some core concepts of blockchains including that they are distributed secure logfiles, how they provide transparency and robustness without central control, and how mining and proof-of-work consensus keeps the network secure.
- It discusses the differences between permissioned and unpermissioned ledgers, and considerations for whether
Gas is a unit used in Ethereum that measures the amount of computational effort required to execute a transaction or smart contract. Every operation on the Ethereum network has an associated gas cost. While gas is used to measure computational work, fees are actually paid in ether using a gas price. The total fee paid is calculated as gas used multiplied by gas price. Gas ensures transactions pay appropriately for their computational requirements and prevents spam on the network. Running out of gas results in transaction failure, while providing too little gas price means a transaction won't be included in a block.
After an explosion of altcoins and funding, technical constraints and regulatory angst have taken over the headlines. Still, the frenzy of the past two years set the stage for the next wave of adoption with a steady inflow of talent and new, uniquely compelling use cases of digital assets.
Ethereum's Casper protocol is a proof of stake algorithm that aims to address issues with proof of work consensus. It implements a hybrid POW/POS model initially called Casper FFG to ease the transition from proof of work to proof of stake. Under Casper, validators stake ether to validate blocks, and receive rewards proportionate to their bets. However, malicious validators who try to undermine the network through actions like "nothing at stake" attacks will face penalties like slashing their entire staked amount. This approach provides stronger incentives for honest participation than proof of work alone. In the future, Ethereum plans to fully transition to a pure proof of stake model with Casper CBC, which uses a formal "correct by construction
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Blockchain - A Catalyst for Solving Age-old Distributed Systems Problems
1. Dilum Bandara, PhD
Dept. of Computer Science & Engineering,
University of Moratuwa
Colombo Blockchain Dev Meetup, Sep 4, 2018
2. 2
ID Assets
Alice 500
Bob 1,000
Peter 500
Rani Plot 123 @ Col 7
Rasa
Mango
Polonnaruwa,
Org. #45781
ID Assets
Alice 500
Bob 1,000
Peter 500
Rani Plot 123 @ Col 7
Rasa
Mango
Polonnaruwa,
Org. #45781
ID Assets
Alice 500
Bob 1,000
Peter 500
Rani Plot 123 @ Col 7
Rasa
Mango
Polonnaruwa,
Org. #45781
ID Assets
Alice 500
Bob 1,000
Peter 500
Rani Plot 123 @ Col 7
Rasa
Mango
Polonnaruwa,
Org. #45781
3. 3
ID Assets
Alice 500
Bob 1,000
Peter 500
Rani Plot 123 @ Col 7
Rasa
Mango
Polonnaruwa,
Org. #45781
ID Assets
Alice 500
Bob 1,000
Peter 500
Rani Plot 123 @ Col 7
Rasa
Mango
Polonnaruwa,
Org. #45781
ID Assets
Alice 500
Bob 1,000
Peter 500
Rani Plot 123 @ Col 7
Rasa
Mango
Polonnaruwa,
Org. #45781
ID Assets
Bob 1,000
Peter 500
Rasa
Mango
Polonnaruwa,
Org. #45781
ID Assets
Alice 500
Peter 500
Rani Plot 123 @ Col 7
Rasa
Mango
Polonnaruwa,
Org. #45781
ID Assets
Alice 500
Bob 1,000
Rani Plot 123 @ Col 7
4. 4
ID Assets
Alice 500
Bob 1,000
Peter 500
A
ID Assets
Alice
Bob
Peter 500
B
ID Assets
Alice 200 500
Bob 1,300 1,000
Peter 500
P
Transfer 300 to Bob
200 500
1,300 1,000
• Alice may initiate request from
her node or any other node
• No of messages increase with no
of ledger copies
5. 5
ID Assets
Alice 500
Bob 1,000
Peter 500
A
ID Assets
Alice
Bob
Peter 500
B
ID Assets
Alice 500
Bob 1,000
Peter 500
P
Transfer 300 to Bob
200 500
1,300 1,000
• Likeliness of failure increases
with no of ledger copies
6. 6
ID Assets
Alice 500
Bob 1,000
Peter 500
A
ID Assets
Alice 200 500
Bob 1,300 1,000
Peter 500
B
ID Assets
Alice 100 500
Bob 1,000
Peter 900 500
P
Transfer 300 to Bob
• Likeliness of attack increases
with no of ledger copies
7. Blockchain concept focuses on Public-Key Cryptography &
Hashing
Implementation needs to address many distributed system
problems
Timing & Ordering
Consensus
CAP Theorem
Distributed systems research community seems to not care
Lots of others want to solve these problems due to monetary
benefits (e.g., cryptocurrency)
7
8. 8
ID Assets
Alice 200 500
Bob 1,300 1,000
Peter 500
A
ID Assets
Alice 200 500
Bob 1,300 1,000
Peter 500
B
ID Assets
Alice 500
Bob 1,000
Peter 500
P
Transfer 300 to Bob
t = 10 t = 12
Transfer 1,200 to Peter t = 15t = 18
t = 16t = 18
Reject
Accept
• Inconsistent ledger due to
concurrent transactions (TXs)
• Inconsistency increases with no
of ledger copies
9. Use of sender’s time to order TXs not reliable
Clocks aren’t accurate – Drift & skew
Difficult to sync them & keep them synched
Sender could change time to game the system
Global ordering of TXs
Lamport’s time stamp
A logical counter that increments when messages
are send & received
Lamport’s Totally Ordered Multicast
Vector clocks
Address “lower logical clock doesn’t guarantee
happened before relationship” in Lamport’s time stamp
Doesn’t scale with no of ledger copies
9
10. No concurrent TXs related to same account in same block
E.g., Bitcoin, Ethereum, & Hyperledger
Low transaction throughput – 3-6 TX/Sec
Store global state in a database (RDBMS or NO-SQL) & proof of
existence on Blockchain
E.g., Stellar & BigchainDB
Fully or semi-centralized
Not quite Blockchain
Need more scalable concurrent transaction support
High throughput
Low Latency
10
11. 2 Blue armies need to simultaneously attack or retreat
Blue army have to communicate across area controlled by White army
White army area Unreliable communication channel
Goal – 2 blue armies to reach agreement about attacking
11
Source:
www.ee.surrey.ac.uk/Projects/CAL/networks/
Network-Transport_Application_Layers.htm
12. Agreement in the judgment or opinion reached by a
group as a whole
Getting 2 nodes to agree is hard
Getting many nodes to agree is even harder
Achieving consensus under:
Unreliable communication – Partition tolerance
Failed nodes – Fault tolerance
Misbehaving nodes – Byzantine fault tolerance
12
13. 13
I have a plan – Let’s attack at dawn tomorrow
Splendid idea, A! See you at dawn tomorrow!
Received message. We are ready for the battle.
Received acknowledgement. We are also ready
Blue 1
Blue 2
Gotcha,
I lied
14. “It’s impossible for a web service to provide following 3
guarantees at the same time” (Eric Brewer, 2000)
Consistency
Availability
Partition-tolerance
14
ID Assets
Alice 500
Bob 1,300 1,000
Peter 200 500
ID Assets
Alice 500
Bob 1,300 1,000
Peter 200 500
Peter = 200
Peter = 500
15. Nodes loose network
connectivity
Networks will partition!
Partition tolerance is mandatory in
distributed systems
So, choose Consistency or
Availability…
Blockchain needs to be Available
Ledger needs to be Consistent
Consensus Consistency
15
C A
P
Required
16. No guarantee that a TX will be included in next block
Leader election
Selected leader decides on what goes into block
Believe leader’s block/ledger as ground truth
How to elect leader?
Proof of Authority (PoA) – e.g., VeChain, Kovan (Ethereum testnet)
Based on trust – e.g., Stellar
Random leader
Based on votes – e.g., Hyperledger Fabric & Sawtooth
Proof of Stake – e.g., Hyperledger Iroha
Proof of Brain – Steem
Fast
Consistency depends on leader
16
17. Proof of Work
Believe 1st one that solves a given puzzle
Puzzle should be difficult to compute (no short-cuts), but easy check
E.g., calculating a hash with specific no of 0/1 bits
Anyone can compete & difficult to game
Slow & expensive
Multiple truths may exist for a while
Longest chain wins
New truth may replace current truth Some TXs need to be reversed
E.g., wait for 6 blocks in Bitcoin to confirm a TX
TXs need to be fast, persistent, & low cost
17
18. Low-latency TX processing
Inclusion guarantees
Fast confirmations
Persistence
High-throughput Concurrent TX processing
Low cost
Truly distributed ledger
Beyond proof of existence 18
Distributed
System
Problems
Blockchain
Working systems used & contributed by many
But
Slow
No guarantees
High cost
Not scalable