Blockchain

from Wikipedia, the free encyclopedia
The determining blockchain (black) consists of the longest sequence of blocks starting from the origin to the current block. Alternative chains are orphaned (purple) as soon as they are shorter than another chain.

A block chain (also block chain, English for block chain ) is a continuously expandable list of records , "blocks" which are sold by means of cryptographic processes are chained together. Each block typically contains a cryptographically secure hash (scatter value) of the previous block, a time stamp and transaction data .

The term blockchain is also used when an accounting system is managed in a decentralized manner and the correct status must be documented because many participants are involved in the accounting. This concept is referred to as distributed ledger technology (decentralized account book technology) or DLT. What is to be documented is irrelevant for the term blockchain. It is crucial that later transactions build on earlier transactions and confirm them as correct by proving knowledge of the earlier transactions. This makes it impossible to manipulate or erase the existence or content of earlier transactions without destroying all subsequent transactions as well. Other participants in the decentralized accounting, who still have knowledge of the later transactions, would recognize a manipulated copy of the blockchain by the fact that it has inconsistencies in the calculations.

The process of cryptographic chaining in a decentralized accounting system is the technical basis for crypto currencies , but can also contribute to improving or simplifying transaction security in distributed systems compared to central systems. One of the first applications of blockchain is the cryptocurrency Bitcoin .

The way it works is similar to the journal of bookkeeping . It is therefore also known as the “Internet of value”. A blockchain enables an agreement to be reached between the nodes in a decentralized network . (See also: Byzantine Error .)

“The basic idea of ​​the notch stick is extremely simple: In this technique, which is as primitive as it is ingenious, two sticks are placed next to each other and scratched at right angles, with each notch corresponding to a guilt. The creditor takes one stick, the debtor the other. The creditor will not be able to add a notch and the debtor will not be able to eliminate one, since comparing the two sticks would immediately reveal the forgery.
Pretty easy right? An ancient, but also very modern technology. Because the blockchain - this invention, which appears to us to be the greatest novelty of our time - is nothing more than a worldwide score that has been extended to countless computers. Instead of a counting stick shared by two people, we are dealing with a track that is stored on as many hard drives as possible to prevent adding or deleting tracks (blocks). Once again, technology brings ancient things back to light, as if in a procession.
The blockchain may help us to solve many problems - but we can assume that it will also create many new problems. "

- Maurizio Ferraris

history

The first basics for cryptographically secured chaining of individual blocks were described in 1991 by Stuart Haber and W. Scott Stornetta , in 1996 by Ross J. Anderson and in 1998 by Bruce Schneier and John Kelsey . In 1998 Nick Szabo also worked on a mechanism for a decentralized digital currency that he called "Bit Gold". In 2000, Stefan Konst developed a general theory on cryptographically secured chains and derived various solutions for implementation.

The concept of the block chain as a distributed database management system was first in 2008 by Satoshi Nakamoto in white paper to Bitcoin described. The following year he published the first implementation of the Bitcoin software and thereby started the first publicly distributed blockchain.

properties

New blocks are created using a consensus procedure and then attached to the blockchain. The most popular consensus method is the proof-of-work method; However, there are numerous other ways of establishing consensus ( Proof of Stake , Proof of Capacity , Proof of Burn , Proof of Activity ). Due to the successive storage of data in a blockchain, they cannot be changed subsequently without damaging the integrity of the overall system. This makes the manipulation of data much more difficult. The decentralized consensus mechanism replaces the need for a trustworthy third party to confirm the integrity of transactions.

Concatenation principle
A blockchain is a chained sequence of data blocks that is updated over time.
Decentralized storage
A blockchain is not stored centrally, but managed as a distributed register. All those involved save their own copy and update it.
Consensus mechanism
It must be ensured that an identical chain is created for all parties involved. For this purpose, suggestions for new blocks must first be developed. This is done by validators (which Bitcoin calls "miners"). Then the participants have to agree which proposed block will actually be added to the chain. This is done using a so-called consensus protocol, an algorithmic process for voting.
Tamper-proof
By cryptographic methods to ensure that the block chain can not be changed later. The chain of blocks is therefore unchangeable, forgery-proof and tamper-proof.
Transparency / confidentiality
The data stored on the blockchain can be viewed by everyone involved. However, they are therefore not necessarily readable for everyone, because content can be stored in encrypted form. Blockchains thus allow a flexible configuration of the degree of confidentiality.
Non-repudiation
Through the use of digital signatures , information can be saved in the blockchain, which proves in a forgery-proof manner that participants have undeniably stored certain data, such as initiated transactions.

Application example Bitcoin

Simplified Bitcoin blockchain

With Bitcoin , a blockchain consists of a series of data blocks , in each of which one or more transactions are summarized and provided with a checksum , i.e. That is, they are combined in pairs to form a hash tree . The root of the tree (also called Merkle root or top hash ) is then saved in the associated header . The entire header is then also hashed ; this value is saved in the following header. This ensures that no transaction can be changed without changing the associated header and all subsequent blocks as well.

Bitcoin's blockchain is the oldest blockchain. It started in January 2009, had a size of approx. 221.846 GB at the beginning of June 2019 and was redundant and publicly accessible on approx. 9,516 nodes on June 5, 2019.

Application example auditing

When auditing in information technology , it is important to record safety-critical operations of software processes. This applies in particular to access to and modification of confidential or critical information. Auditing is suitable for a blockchain because it produces relatively small amounts of data and at the same time has high security requirements.

A blockchain can protect the audit log (also known as the audit trail ) from changes. In addition, the individual entries should be provided with a digital signature to guarantee authenticity. A decentralized consensus mechanism, as with Bitcoin , is not absolutely necessary.

Since, on the one hand, confidential information is stored and, on the other hand, no element of the blockchain can be deleted without making it invalid, the individual entries can also be encrypted . Since the implementation of blockchains is currently (as of May 2017) very complex due to the lack of easy-to-use implementations, its use is only recommended for information that is particularly worthy of protection.

Examples of use are auditing of systems for medical information (e.g. electronic health records ), contracts and monetary transactions with high financial value, military secrets, legislation and electronic voting , the security management of critical systems or data from large companies that are subject to the Sarbanes Oxley Act or similar directives are covered.

As announced in July 2018, the four auditing companies Deloitte , KPMG , PricewaterhouseCoopers International and Ernst & Young are testing a blockchain service for auditing the interim reports of public companies. The aim is to give auditing companies the opportunity to track business processes in a decentralized manner using a traceable and tamper-proof data chain, thereby optimizing and automating the confirmation process.

Application example capital markets

The blockchain is also being considered as an application in the capital markets . The R3 consortium has published the Corda platform with several financial institutions , which is intended to represent a substructure for blockchain applications for capital markets. The platform is to be used as a pilot project for the E-Krona of the Swedish Reichsbank , in cooperation with Accenture , until 2021 .

The largest areas of application for capital markets are in the area of ​​the settlement of shares and other financial instruments, the issuing of syndicated loans and the financing of companies with equity.

Application example supply chains for food

The use of a blockchain, in which the parties involved jointly document the transactions in the supply chain, can enable significant cost and time savings. A blockchain could lift the mistrust of a central register-keeping actor, since a blockchain register is accessible to all participants. The bookkeeping and reading rights can be distributed in stages, adapted to the different user groups and their needs, such as manufacturers, freight forwarders, customs and different consumers. This means that there is no complete transparency that competitors could take advantage of. For example, end consumers can only be granted reading rights, with the aid of which the origin and the entire supply chain from harvest to processing, logistics, customs clearance, certification, food monitoring, wholesalers and retailers can be traced in a transparent and verifiable manner.

There is also potential for automation for the documentation obligations to be complied with: For example, a sensor installed in the container could measure the temperature of food, write the measurement data to the blockchain and thus document seamless compliance with the cold chain . If it were not adhered to, an appropriately set up smart contract could automatically sound the alarm.

Criticism / assessments

For years there has been public criticism from experts who question the security and usability of blockchain. The most frequently criticized are the low efficiency of the long data chains and the high energy consumption in the proof-of-work process, which is often used to generate a new valid block . In addition to technical criticism from the developer side, experts from the business and financial world also warn of euphoria for a "solution" that lacks the problem. In its 2019 report, the German Expert Commission for Research and Innovation sees blockchain technology as having "high potential benefits for companies, the population and administration". Possible applications include international supply chains and electricity trading.

literature

  • Daniel Drescher: Blockchain Basics. An introduction to the elementary concepts in 25 steps (translation from English by Guido Lenz) . mitP Verlags GmbH & Co. KG, Frechen 2017, ISBN 978-3-95845-653-2 .
  • Stuart Haber, W. Scott Stornetta: How to Time-Stamp a Digital Document . In: Advances in Cryptology - Crypto '90. Lecture Notes in Computer Science v. 537 . Springer-Verlag, Berlin 1991, ISBN 978-3-540-38424-3 , p. 437-455 , doi : 10.1007 / 3-540-38424-3_32 .
  • Ross J. Anderson: The Eternity Service . In: Pragocrypt . 1996.
  • Bruce Schneier, John Kelsey: Cryptographic Support for Secure Logs on Untrusted Machines . In: The Seventh USENIX Security Symposium Proceedings . USENIX Press, January 1998, pp. 53-62 .
  • Primavera De Filippi , Aaron Wright: Blockchain and the Law: The Rule of Code . Harvard University Press, Cambridge, MA 2018, ISBN 978-0-674-97642-9 .

Web links

Wiktionary: Blockchain  - explanations of meanings, word origins, synonyms, translations

items

lectures

Podcasts

Lectures

additional

Individual evidence

  1. ↑ a b Economist Staff: Blockchains: The great chain of being sure about things. In: The Economist . October 31, 2015, accessed on June 18, 2016 : “The technology behind bitcoin lets people who do not know or trust each other build a dependable ledger. This has implications far beyond the crypto currency. "
  2. ↑ David Z. Morris: Leaderless, Blockchain-Based Venture Capital Fund Raises $ 100 Million, And Counting. In: Fortune.com. May 15, 2016, accessed May 23, 2016 .
  3. ^ Nathan Popper: A Venture Fund With Plenty of Virtual Capital, but No Capitalist. In: New York Times . May 21, 2016. Retrieved May 23, 2016 .
  4. ↑ Jerry Brit, Andrea Castillo: Bitcoin: A Primer for Policymakers. Mercatus Center, George Mason University, 2013, accessed October 22, 2013 .
  5. ^ Trottier, Leo: original bitcoin. In: github.com. June 18, 2016, accessed on June 18, 2016 : "This is a historical repository of Satoshi Nakamoto's original bit coin sourcecode"
  6. ↑ a b Arvind Narayanan, Joseph Bonneau, Edward Felten, Andrew Miller, Steven Goldfeder: Bitcoin and cryptocurrency technologies: a comprehensive introduction . Princeton University Press, Princeton 2016, ISBN 978-0-691-17169-2 .
  7. ↑ Jörn Heckmann: Programmed contracts as the future of the blockchain . In: com! No. 2/2017 , p. 100 .
  8. ↑ Blockchain #Banking: a guide to the Distributed Ledger approach and application scenarios ( Memento from December 22, 2017 in the Internet Archive ) / Ed .: Bundesverband Informationswirtschaft, Telekommunikation und neue Medien. - Berlin, 2016 [accessed December 19, 2017]
  9. ↑ Maurizio Ferraris : What is capital? What about the money? What does the blockchain do? A look into the Neolithic yields astonishing answers - the blockchain is not a radical novelty, it continues an old analog technology. It starts with a piece of wood that already does in many ways what the new technology promises. NZZ 17.12.18
  10. ↑ a b Stefan Konst: Secure log files based on cryptographically linked entries. (PDF) August 9, 2000, accessed October 15, 2016 .
  11. ^ Nathaniel Popper: Decoding the Enigma of Satoshi Nakamoto and the Birth of Bitcoin. In: nytimes.com. New York Times, May 15, 2015, accessed November 29, 2016 .
  12. ↑ IT supplement on blockchain: A brief history of blockchain . In: Chartech magazine . No. 210, July / August 2017, p. 5 reference to supplement, article on p. 4 of the supplement. Retrieved September 27, 2017.
  13. ↑ Bitcoin: A Peer-to-Peer Electronic Cash System. In: bitcoin.org. October 2008, accessed May 14, 2016 .
  14. ↑ Bitcoin Developer Guide - Mining. In: Bitcoin Developer Guide. The Bitcoin Foundation, accessed on September 22, 2014 (English): "Mining adds new blocks to the block chain, making transaction history hard to modify."
  15. ↑ Blockchain. In: Jens Fromm, Mike Weber (eds.): ÖFIT trend show: Public information technology in the digitized society. Competence Center Public IT, Berlin 2016, ISBN 978-3-9816025-2-4 .
  16. ↑ acatech - German Academy of Science and Engineering (ed.): Acatech HORIZONTE: Blockchain . Munich 2018, p. 13 .
  17. ↑ Bitcoin Developer Guide - Block Chain Overview. In: Bitcoin Developer Guide. The Bitcoin Foundation, accessed on November 10, 2016 (English): "A block of one or more new transactions is collected into the transaction data part of a block. Copies of each transaction are hashed, and the hashes are then paired, hashed, paired again, and hashed again until a single hash remains, the merkle root of a merkle tree. The merkle root is stored in the block header. Each block also stores the hash of the previous block's header, chaining the blocks together. This ensures a transaction cannot be modified without modifying the block that records it and all following blocks. "
  18. ↑ Blockchain Size. Retrieved June 5, 2019 .
  19. ^ Coin Dance. Accessed June 5, 2019 .
  20. ↑ a b Blockchain: A game changer for audit processes. Retrieved September 14, 2018 .
  21. ↑ All 'Big Four' Auditors to Trial Blockchain Platform for Financial Reporting. July 19, 2018, accessed September 14, 2018 .
  22. ↑ How Blockchain Is Reshaping External Audit: Crypto Developments by PwC, KPMG, EY and Deloitte. July 26, 2018, accessed September 14, 2018 .
  23. ↑ Philipp Anz: Sweden is testing the E-Krona. In: inside-it.ch. February 21, 2020, accessed February 22, 2020 .
  24. ↑ acatech - German Academy of Science and Engineering (ed.): Acatech HORIZONTE: Blockchain . Munich 2018, p. 26 .
  25. ↑ Erin Griffith: 187 Things the Blockchain Is Supposed to Fix . In: Wired . May 25, 2018, ISSN  1059-1028 ( wired.com [accessed January 28, 2019]).
  26. ↑ A solution that lacks the problem. The global financial industry has not yet been able to do much with the technology known as blockchain. […] The project was shelved because banks and other potential users believed the same results could be achieved more cheaply using current technology. [...] Basically, it became a solution in the search for a problem. Wall Street rethinks blockchain projects as euphoria meets reality. March 27, 2018, accessed January 28, 2019 .
  27. ↑ Certainly, there is a growing sense that blockchain is a poorly understood (and somewhat clunky) solution in search of a problem. Blockchain's Occam problem. January 2019, accessed on January 28, 2019 .
  28. ↑ see Expert Commission Research and Innovation: Expert Opinions on Research, Innovation and Technological Performance in Germany 2019, pages 80–90 PDF, accessed on August 27, 2019