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Birdie Daniel

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Problemi di sicurezza e vulnerabilità nella blockchain

Indubbiamente, la tecnologia blockchain ha visto un diffuso adattamento negli ultimi anni. Oltre all'adattamento iniziale alle criptovalute, oggi viene utilizzato nel settore sanitario, immobiliare, contatti intelligenti, ecc. Tuttavia, l'implementazione impropria della tecnologia è stata anche la causa di molti problemi di sicurezza della blockchain. Ciò può rendere vulnerabile la blockchain, consentendo agli aggressori di eseguire diverse attività dannose. Come ritardare il funzionamento della catena, invertire le transazioni effettuate sulla blockchain, rubare le chiavi private degli utenti e molto altro.

Questo blog include spettacolo

Ad esempio, recentemente il prezzo di " Safedollar " (un tipo di criptovaluta stablecoin) che doveva sempre essere di valore fisso rispetto al dollaro è sceso a zero a causa di un attacco informatico. I rapporti preliminari mostrano che gli hacker hanno sfruttato una falla nell'algoritmo della moneta. Inoltre, i problemi di sicurezza della blockchain possono avere ripercussioni più ampie per le applicazioni utilizzate da questa tecnologia.

Questo articolo spiega cos'è una blockchain e alcuni dei principali problemi di sicurezza della blockchain. Sono anche menzionati i mezzi per prevenire questi problemi.

Cos'è una Blockchain?

Il dizionario Merriam-Webster definisce blockchain come,

Per dirla in termini semplici, consideralo come un gigantesco database distribuito. Un database che cresce nel tempo con le transazioni e in cui i record precedenti sono immutabili.

Poiché il database è distribuito, nodi diversi possono avere opinioni diverse sui record al suo interno. Ciò potrebbe aver sollevato seri problemi in una blockchain così tanto che la tecnologia potrebbe non essere nemmeno sopravvissuta.

Ma questo problema è stato risolto utilizzando la crittografia, più precisamente le funzioni hash che garantiscono una firma univoca per ogni blocco della catena. Quindi ogni utente sulla blockchain ora può verificare e concordare in modo indipendente sugli stessi record.

Sebbene il problema di cui sopra fosse di natura fondamentale, altri problemi di sicurezza della blockchain potrebbero sorgere in una blockchain funzionante.

Funzionamento della tecnologia Blockchain

Spesso i termini " blockchain " e " criptovaluta " sono usati come sinonimi, ma le due cose sono abbastanza diverse. Le criptovalute sono le applicazioni più popolari della tecnologia blockchain. Questa tecnologia ha trovato pian piano le sue applicazioni anche in altri settori.

Quindi, per spiegare come funziona la blockchain, ecco l'esempio delle criptovalute.

Diciamo che Elon vuole inviare a Jeff una moneta chiamata moneta Astra sulla blockchain. Quindi la prima cosa che devi capire è la crittografia a chiave pubblica. Se non lo conosci, leggilo e torna a questo articolo.

Per dirla in parole povere, possedere una moneta crittografica significa fondamentalmente avere una coppia di chiavi associata a quella moneta. Ora, per eseguire la transazione, Elon avrà bisogno delle seguenti cose:

  • La chiave privata associata alla moneta Astra posseduta da Elon
  • L'indirizzo di Elon sulla blockchain (la sua chiave pubblica)
  • L'indirizzo di Jeff sulla blockchain (la sua chiave pubblica)
  • e, naturalmente, l'importo dovrebbe essere presente con Elon che desidera inviare.

Immagine: come funziona la blockchain

Un semplice esempio

Per inviare una moneta Astra, Elon autorizzerà la transazione firmandola con la sua chiave privata. Successivamente, questo messaggio verrà trasmesso in rete.

Ora, i nodi sulla rete vedranno questo messaggio e lo verificheranno tramite la chiave pubblica di Elon (è così che funziona la coppia di chiavi). Dopo aver verificato l'autenticità del messaggio, i nodi vedranno anche se una moneta è presente all'indirizzo del mittente per evitare problemi di sicurezza della blockchain di base. Verrà quindi raggruppato con un mucchio di altre transazioni.

Ora entra in scena, ' Minatori '. Starebbero lavorando per trovare l'hash crittografico valido per questo gruppo di transazioni che lo trasformerebbe in un blocco .

Ad esempio, nel caso della moneta Astra, un blocco valido è quello il cui cancelletto termina con l'alfabeto ' a '. Quindi, i minatori aggiungerebbero un numero casuale chiamato nonce al gruppo di transazioni. Continuerebbero a cambiare il nonce fino a quando l'hash dell'intero gruppo non finisce con l'alfabeto " a " (è un successo e una prova). Una volta trovato, sarebbe chiamato blocco valido e propagato sulla rete. Quindi quel blocco verrebbe aggiunto alla blockchain e la transazione sarebbe completa.

Ora lo stesso processo si ripeteva più e più volte, aggiungendo nuovi blocchi alla catena. Naturalmente, ci sono altre sfumature come la commissione del minatore, le divisioni del portafoglio, ecc. Che possono essere ignorate fin d'ora per comprendere il funzionamento di base di una blockchain.

Ora, se pensi obiettivamente al di fuori del framework della criptovaluta, una blockchain funziona tramite il consenso dei suoi partecipanti . La prova del lavoro definisce quali record entrano nella blockchain e al suo interno c'è la crittografia, responsabile della fiducia nella blockchain.

6 tipi di attacchi alla blockchain

Sebbene la tecnologia blockchain utilizzi un registro immutabile, ci sono alcuni problemi di sicurezza blockchain che possono minacciare anche la natura di base della tecnologia. Diamo ora un'occhiata ad alcuni di loro uno per uno.

1. 51% di attacchi

Come abbiamo discusso sopra, i miner svolgono un ruolo chiave nella convalida delle transazioni sulla blockchain e quindi la aiutano a crescere ulteriormente. La tecnologia Blockchain prende decisioni in base al supporto popolare . Ad esempio, a volte vengono estratti due blocchi contemporaneamente con transazioni in conflitto. In tal caso, il blocco che ottiene l'approvazione della maggioranza sulla rete viene mantenuto nella catena e l'altro diventa obsoleto.

Ora, se un gruppo di hacker malintenzionati riesce a ottenere il controllo su oltre il 51% o più della potenza di mining, i risultati possono essere disastrosi. Gli hacker possono quindi utilizzare la loro posizione di maggioranza per annullare transazioni ed eseguire transazioni fraudolente. Potrebbero anche essere in grado di riscrivere alcuni blocchi, ma riscrivere l'intera blockchain (sebbene teoricamente possibile) sarebbe praticamente impossibile.

È più probabile che problemi di sicurezza blockchain come l'attacco del 51% si verifichino nelle prime fasi della catena. In un momento in cui sulla rete sono presenti pochissimi miner, sarebbe possibile impadronirsi del 51% della potenza mineraria.

Sibilla Attacchi

Prende il nome da un personaggio famoso del libro, in questo tipo di attacco, un utente malintenzionato crea più falsi nodi sulla rete. Utilizzando questi nodi l'attaccante può ottenere il consenso della maggioranza e ostacolare le transazioni sulla catena. Quindi, un attacco Sybil su larga scala non è altro che l'attacco del 51%.

Per problemi di sicurezza blockchain come gli attacchi Sybil, molti blockchain utilizzano algoritmi proof of work e proof of stake . Sebbene questi algoritmi non prevengano del tutto tali attacchi, ma semplicemente rendano impossibile per l'attaccante eseguirli.

2. Attacchi a doppia spesa

Una caratteristica importante del contante fisico è che non puoi pagare utilizzando la stessa fattura in due luoghi diversi (a meno che tu non sia un mago o un truffatore). Al contrario, le risorse digitali possono essere facilmente replicate, dopotutto sono solo bit di 1 e 0.

Quindi, nell'esempio sopra, Elon può provare a inviare la stessa moneta Astra a due indirizzi di portafoglio diversi, rispettivamente di Jeff e Mark. Questo tipo di attacco sarebbe chiamato attacco a doppia spesa.

In generale, ci sono meccanismi costruiti nella blockchain per prevenire questo tipo di attacchi. Ad esempio, se la moneta viene inviata a Jeff nel primo blocco, la transazione a Mark verrà ignorata nei blocchi successivi.

Ma nel caso in cui entrambe le transazioni siano arrivate a due diversi blocchi estratti contemporaneamente, il blocco con il maggior numero di conferme dai nodi della rete verrà mantenuto e l'altro verrà ignorato dopo un po' di tempo. Tuttavia, questa mitigazione dei problemi di sicurezza blockchain come gli attacchi a doppia spesa ha i suoi svantaggi.

Ad esempio, Mark si aspetterebbe ancora una moneta Astra nel suo portafoglio. Di conseguenza, generalmente, gli utenti aspettano che vengano estratti almeno altri 6 blocchi (come suggerito da Satoshi Nakamoto nel suo white paper ) prima di essere veramente sicuri di ottenere la moneta. Inoltre, se un attaccante motivato è in grado di eseguire un attacco del 51% percento come menzionato sopra, può facilmente eseguire l'attacco a doppia spesa in seguito.

3. Instradamento degli attacchi

Una cosa che possiamo facilmente vedere ormai è che la tecnologia blockchain richiede una rete robusta per funzionare. Gli ISP si connettono tra loro e condividono le informazioni sul percorso tramite il BGP (Border Gateway Protocol). Questo protocollo è vecchio e presenta alcune vulnerabilità che un utente malintenzionato può sfruttare.

Ad esempio, un utente malintenzionato che controlla un ISP può pubblicare un percorso falso e quindi negare le transazioni per alcuni nodi o addirittura dividere a metà la rete blockchain!

Supponiamo, nell'esempio precedente, che il nodo di Elon si trovi in ​​100.0.0.0/16 (/16 è il prefisso IP). Ora, se un utente malintenzionato propaga un percorso a 100.0.0.0/17 tramite il BGP, presto queste informazioni verranno aggiornate in tutti i router (è così che funziona BGP condividendo le informazioni sul percorso con i vicini). Di conseguenza, i dati destinati a Elon verranno deviati alla voce specificata dall'attaccante.

Questo perché quando a BGP vengono presentati due percorsi in conflitto (100.0.0.0/16 di Elon vs 100.0.0.0/17 dell'attaccante), seleziona quello con un prefisso più lungo.

I problemi di sicurezza della blockchain relativi al routing possono avere gravi implicazioni poiché nel 2014 un hacker è riuscito a eseguire l'attacco di routing. Ciò ha consentito all'hacker di impedire la propagazione sulla rete dei blocchi estratti dai minatori. Invece, ha utilizzato le informazioni per rivendicare il lavoro svolto come proprio e quindi è stato ricompensato con commissioni minerarie.

4. Attacchi alla sicurezza con chiave privata

Come accennato in precedenza, la crittografia a chiave pubblica è al centro della tecnologia blockchain. Pertanto, l'implementazione o la gestione impropria della crittografia a chiave pubblica può causare alcuni seri problemi di sicurezza della blockchain.

Se la firma della chiave è implementata male nella tua blockchain (ad esempio usando la stessa chiave per firme multiple invece di un albero Merkle), può consentire a un utente malintenzionato di ottenere la tua chiave privata dalla chiave pubblica. Avere il controllo della tua chiave privata significa sostanzialmente possedere tutti i dati a te associati in una blockchain.

Nel caso delle criptovalute, possedere tutte le tue monete. Tuttavia, le possibilità che ciò accada sono molto minori a meno che non utilizzi un codice davvero buggato per la tua blockchain. Il problema principale è la gestione impropria della tua chiave privata. Ad esempio, archiviarlo in computer infetti, paste pubbliche, ecc. Nel 2020 sono stati hackerati circa $ 300.000 di criptovaluta perché l'utente ha lasciato la chiave pubblica in Evernote.

5. Attacchi minerari egoistici

Un attacco minerario egoistico è esattamente quello che sembra.

Supponiamo che Jeff stia inviando poche monete Astra a Mark con un ritardo in modo tale che le transazioni separate si trasformino in più blocchi diversi (con un sacco di altre transazioni da parte di persone che si scambiano monete). Nel frattempo, Elon e Bill sono in competizione come minatori per convalidare queste transazioni.

Supponiamo ora che Elon scopra il blocco valido per la prima transazione ma invece di propagarlo sulla rete, inizi a lavorare per trovare il secondo blocco valido per le transazioni successive. Continua a creare la sua catena di blocchi segreta fino a quando la blockchain principale non è un blocco dietro la sua catena segreta. È allora che rivela strategicamente la sua catena alla rete.

Poiché alcuni protocolli blockchain sono progettati, nel caso di due fork in conflitto viene mantenuta la catena più lunga. Quindi, Elon ora può richiedere una commissione mineraria più alta.

Al contrario, se Elon avesse pubblicato il blocco valido non appena lo avesse trovato, lui e Bill avrebbero iniziato a competere dallo stesso livello per il blocco successivo.

Pertanto, nell'attacco minerario egoistico, un attaccante usa la sua posizione di vantaggio per mantenerla più a lungo per massimizzare i profitti. Tuttavia, questa strategia è anche rischiosa. Se Bill o qualche altro minatore avesse trovato il blocco successivo prima di Elon e lo avesse pubblicato, tutto il suo lavoro sarebbe stato inutile.

A prima vista sembra rischioso e non redditizio, ma un'analisi che utilizza le catene di Markov ha dimostrato che il mining egoistico funziona davvero!

6. Contatti intelligenti vulnerabili

I contatti intelligenti sono fondamentalmente accordi scritti in codice che utilizzano blockchain per la registrazione.

Ad esempio, nella vita reale, se presti del denaro a qualcuno, ricevi un interesse periodico fino al termine del periodo di prestito, dopodiché ti restituisci l'importo principale.

Ora, questo può essere tradotto in codice e utilizzando la criptovaluta al posto del denaro reale. La cosa buona è che non hai bisogno di intermediari come una banca. Una volta che il contratto è in essere, non c'è modo di cambiarlo.

Tuttavia, a volte questi contatti sono codificati male. Ciò consente a un utente malintenzionato di trovare potenziali difetti nel codice e sfruttarli. Questo è stato visto nel caso di DAO, quando un attaccante è stato in grado di trovare un tale difetto e rubare 50 milioni di dollari di criptovaluta.

Prevenire i problemi di sicurezza della blockchain

  • L'uso di Proof of Stake invece di Proof of Work può aiutare a prevenire gli attacchi del 51%. Poiché la decisione sarà presa dagli utenti che hanno già il controllo della maggior parte delle monete.
  • Esistono numerosi algoritmi per prevenire gli attacchi di Sybil. Uno dei quali chiamato Proof of Work è implementato nella maggior parte delle criptovalute.
  • È importante tenere sotto controllo i pool minerari della tua blockchain. Assicurati che qualsiasi pool che viola un limite del 40%, dirotti alcuni dei suoi miner verso altri pool.
  • L'uso di protocolli di routing sicuri (uno con certificati) può aiutare a prevenire gli attacchi di routing sulla blockchain.
  • I contatti intelligenti devono essere accuratamente controllati per eventuali bug da esperti prima dell'implementazione.
  • Costruisci una solida comunità dei tuoi utenti blockchain e aggiornali tramite e-mail, newsletter, ecc. per quanto riguarda pratiche di archiviazione sicura delle chiavi private.

Infine, si può affermare che la blockchain è davvero una tecnologia molto rivoluzionaria che ha fuso l'intero esercizio della costruzione del consenso con il rigore del codice. Una blockchain è sicura quanto il suo codice sottostante. Pertanto, prima di rendere pubblica la tua blockchain, esegui test e audit approfonditi per eventuali problemi di sicurezza della blockchain. All'aumentare del valore finanziario della tua blockchain, aumentano anche gli attacchi su di essa. Sebbene un audit di sicurezza blockchain possa sembrare costoso, non è nulla in confronto alle perdite che potresti dover affrontare se si verifica uno sfortunato attacco sulla tua app basata su blockchain. Regolari e approfonditi controlli di sicurezza e pentest impediranno che la tua blockchain diventi defunta in futuro.

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Devin Pinto

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Blockchain Certification | Blockchain Training Course | Blockchain Council

In all the market sectors, Blockchain technology has contributed to the redesign. The improvements that were once impossible have been pushed forward. Blockchain is one of the leading innovations with the ability to influence the various sectors of the industry. It also has the ability to be one of the career-influencing innovations at the same time. We have seen an increasing inclination towards the certification of the Blockchain in recent years, and there are obvious reasons behind it. Blockchain has everything to offer, from good packages to its universal application and futuristic development. Let’s address the reasons why one should go for Blockchain certification.

5 advantages of certification by Blockchain:

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2. Growing industry- When you select any qualification course, it becomes important that you choose a growing segment or industry that promises potential in the future. You should anticipate all of these with Blockchain. The size of the blockchain market is expected to rise from USD 3.0 billion in 2020 to USD 39.7 billion by 2025. This will see an incredible 67.3 percent CAGR between 2020-2025. To help business processes, several businesses are outsourcing Blockchain technologies. This clearly demonstrates that there will be higher demand in the future for Blockchain developers and certified Blockchain professionals.

3. Universal application- One of the major reasons for the success of Blockchain is that it has a global application. It is not sector-specific. Blockchain usage cases are discovered by almost all market segments. In addition, other innovations such as AI, big data, data science and much more are also supported by Blockchain. It becomes easier to get into a suitable industry once you know about Blockchain.

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**5.**After a certain point of your professional life, you are expected to learn about new abilities that can help enhance your skills. Upskilling is paramount. Upskilling oneself has become the need for the hour, and choosing a path that holds a lot of potential for the future is the best way to do this. For all computer geeks and others who want to gain awareness of emerging technology, Blockchain is a good option.

Concluding thoughts- opting for Blockchain certification is a successful career move with all these advantages. You will be able to find yourself in a safe and secured work profile once you have all the knowledge and information. Link for Blockchain certification programme with the Blockchain Council.

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5 Blockchain Applications That Have Transformed the World of Technology

The blockchain is the decentralized database of the blocks of information, which gets recorded in the chain format and linked in a secured crypto graphical manner. This technology ensures proper safety of the data due to its secure nature, and it totally changes how people carry out transactions. It also brings about a faster and secure process of validating information needed to establish reliability.

Though blockchain technology came into the market to carry out only digital transactions, it is now used in various industries like supply chain, finance, health care, and many more.

The blockchain technology has made its position in mobile app development as well. Blockchain applications are transparent and accountable. From getting easy access to medical records and buying insurance, you can see blockchain applications everywhere.

Here are some of the areas where you can see the use of blockchain applications and how they have changed various industries.

1. Ripple

Ripple is useful for increasing banking transactions. The implementation of blockchain technology in the financial sector is much more profound than any other sector. Ripple proves this. It is one of the greatest tools to record and complete financial transactions.

It develops a large network despite strict physical boundaries. As there is no such third-party involvement present, the cost of these transactions is lower than usual. At the same time, the network also remains transparent and quite secured.

It is normally seen that financial transactions that happen globally are

error-prone and take a lot of time. In addition to this, when the transaction

fees and exchange rates get added up, the total cost usually gets high.

However, Ripple offers real-time international transactions without spending too much money. It has the network of about 200+ institutions making the process affordable, secure, and fast for all sorts of international transactions.

2. Etherisc

This blockchain application helps in automating flight insurance. Insurance is another area where blockchain is gaining popularity. Through this application, insurers can make smart contracts rather than getting involved in the traditional contracts that are usually complex. Etherisc is the blockchain application that helps customers buy flight insurance. If the flight gets canceled or delayed, they do not have to wait for months to get the payment back. This application ensures an on-time payout.

#blockchain #blockchain-technology #blockchain-development #blockchain-use-cases #blockchain-a #blockchain-technologies #technology #decentralization

A Collection About Awesome Blockchains

Mining Digital Gold one Block at a Time?! • Don't Expect to Get Insanely Rich (Quick) • Tulips :tulip::tulip::tulip: (like Blockchains) are Great and Gorgeous (and will Endure)

b0 = Block.first(
        { from: "Dutchgrown", to: "Vincent", what: "Tulip Bloemendaal Sunset", qty: 10 },
        { from: "Keukenhof",  to: "Anne",    what: "Tulip Semper Augustus",    qty: 7  } )

b1 = Block.next( b0,
        { from: "Flowers",    to: "Ruben",   what: "Tulip Admiral van Eijck",  qty: 5  },
        { from: "Vicent",     to: "Anne",    what: "Tulip Bloemendaal Sunset", qty: 3  },
        { from: "Anne",       to: "Julia",   what: "Tulip Semper Augustus",    qty: 1  },
        { from: "Julia",      to: "Luuk",    what: "Tulip Semper Augustus",    qty: 1  } )
...

(Source: blockchain_with_transactions.rb)

Awesome Blockchains

A collection about awesome blockchains - open distributed databases w/ crypto hashes incl. git ;-). Blockchains are the new tulips :tulip::tulip::tulip:.

Contents:

What's News?

For blockchain books, see the new Best of Crypto Books page »

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Libra Shrugged: How Facebook Tried to Take Over the Money by David Gerard, November 2020, 182 Pages -- Introduction: Taking over the money ++ A user's guide to Libra ++ The genesis of Libra: Beller's blockchain ++ To launch a Libra: Let’s start a crypto ++ Bitcoin: why Libra is like this ++ The Libra White Papers ++ Banking the unbanked ++ The Libra Reserve plan and economic stability ++ Libra, privacy and your digital identity ++ The regulators recoil in horror ++ David Marcus before the US House and Senate ++ July to September 2019: Libra runs the gauntlet ++ October 2019: Libra's bad month ++ Mark Zuckerberg before the US House ++ November 2019: The comedown ++ Central bank digital currencies ++ Epilogue: Libra 2.0: not dead yet ++ Appendix: 2010–2013: The rise and fall of Facebook Credits

For more about Diem (formerly Libra), see the Awesome Diem (formerly Libra) and Move page »


For crypto quotes, see the new 100+ Best of Crypto Quotes - I HODL, you HODL, we HODL! - BREAKING: BITCOIN JUST BROKE $22 000! page »

The Best Crypto Quote "Oracle Saying" of the Year 2020 Award Goes To...

SEC Investor Education:

  • Don't understand an investment?
  • Don't invest in it.

Yes, but what if there's only 21 million of it?

- Trolly McTrollface

Frequently Asked Questions (F.A.Q.s) & Answers

Q: What's a Blockchain?

A: A blockchain is a distributed database with a list (that is, chain) of records (that is, blocks) linked and secured by digital fingerprints (that is, cryptho hashes). Example from blockchain.rb:

[#<Block:0x1eed2a0
  @timestamp     = 1637-09-15 20:52:38,
  @data          = "Genesis",
  @previous_hash = "0000000000000000000000000000000000000000000000000000000000000000",
  @hash          = "edbd4e11e69bc399a9ccd8faaea44fb27410fe8e3023bb9462450a0a9c4caa1b">,
 #<Block:0x1eec9a0
  @timestamp     = 1637-09-15 21:02:38,
  @data          = "Transaction Data...",
  @previous_hash = "edbd4e11e69bc399a9ccd8faaea44fb27410fe8e3023bb9462450a0a9c4caa1b",
  @hash          = "eb8ecbf6d5870763ae246e37539d82e37052cb32f88bb8c59971f9978e437743">,
 #<Block:0x1eec838
  @timestamp     = 1637-09-15 21:12:38,
  @data          = "Transaction Data......",
  @previous_hash = "eb8ecbf6d5870763ae246e37539d82e37052cb32f88bb8c59971f9978e437743",
  @hash          = "be50017ee4bbcb33844b3dc2b7c4e476d46569b5df5762d14ceba9355f0a85f4">,
  ...

Q: What's a Hash? What's a (One-Way) Crypto(graphic) Hash Digest Checksum?

A: A hash e.g. eb8ecbf6d5870763ae246e37539d82e37052cb32f88bb8c59971f9978e437743 is a small digest checksum calculated with a one-way crypto(graphic) hash digest checksum function e.g. SHA256 (Secure Hash Algorithm 256 Bits) from the data. Example from blockchain.rb:

def calc_hash
  sha = Digest::SHA256.new
  sha.update( @timestamp.to_s + @previous_hash + @data )
  sha.hexdigest   ## returns "eb8ecbf6d5870763ae246e37539d82e37052cb32f88bb8c59971f9978e437743"
end

A blockchain uses

  • the block timestamp (e.g. 1637-09-15 20:52:38) and
  • the hash from the previous block (e.g. edbd4e11e69bc399a9ccd8faaea44fb27410fe8e3023bb9462450a0a9c4caa1b) and finally
  • the block data (e.g. Transaction Data...)

to calculate the new hash digest checksum, that is, the hash e.g. be50017ee4bbcb33844b3dc2b7c4e476d46569b5df5762d14ceba9355f0a85f4.

Q: What's a Merkle Tree?

A: A Merkle tree is a hash tree named after Ralph Merkle who patented the concept in 1979 (the patent expired in 2002). A hash tree is a generalization of hash lists or hash chains where every leaf node (in the tree) is labelled with a data block and every non-leaf node (in the tree) is labelled with the crypto(graphic) hash of the labels of its child nodes. For more see the Merkle tree Wikipedia Article.

Note: By adding crypto(graphic) hash functions you can "merkelize" any data structure.

Q: What's a Merkelized DAG (Directed Acyclic Graph)?

A: It's a blockchain secured by crypto(graphic) hashes that uses a directed acyclic graph data structure (instead of linear "classic" linked list).

Note: Git uses merkelized dag (directed acyclic graph)s for its blockchains.

Q: Is the Git Repo a Blockchain?

A: Yes, every branch in the git repo is a blockchain. The "classic" Satoshi-blockchain is like a git repo with a single master branch (only).

Do-It-Yourself (DIY) - Build Your Own Blockchain

PythonRubyJavaScriptJavaGo

Python

Let's Build the Tiniest Blockchain in Python Series by Gerald Nash

Build Your Own Blockchain: A Python Tutorial by Eric Munsing, March 2017, (Source)

Learn Blockchains by Building One (in Python) by Daniel van Flymen, September 2017, (Source) -- The fastest way to learn how Blockchains work is to build one

Build Your Own Blockchain (in Python 3) Series by Jack Schultz, (Source)

A Practical Introduction to Blockchain with Python by Adil Moujahid, March 2018, (Source)

Ruby

How Does Bitcoin Force Consensus Among Byzantine Generals? by Fabio Akita, November 2017

blockchain-lite - Build your own blockchains with crypto hashes; revolutionize the world with blockchains, blockchains, blockchains one block at a time! by Gerald Bauer, Ruby Advent Calendar 2017 / Day 1, December 2017

merkletree library - Build Your Own Crypto Hash Trees; Grow Your Own Money on Trees by Gerald Bauer, Ruby Advent Calendar 2017 / Day 19, December 2017

centralbank command line tool (and library) - Print Your Own Money / Cryptocurrency; Run Your Own Federated Central Bank Nodes on the Blockchain Peer-to-Peer over HTTP by Gerald Bauer, Ruby Advent Calendar 2017 / Day 24, December 2017

A guide to building a blockchain & cryptocurrency from scratch (Source) by Antoine Fink, April 2021

Crystal

Write your own blockchain and Proof-of-Work (PoW) algorithm using Crystal by Bradford Lamson-Scribner, May 2018, (Source)

JavaScript

Writing a Tiny Blockchain in JavaScript by Xavier Decuyper, July 2017

Node.js Blockchain Imlementation: BrewChain: Chain+WebSockets+HTTP Server by Darren Beck, November 2017, (Source) -- Protecting the tea making ledger from unscrupulous colleagues

Build your own Blockchain in Javascript/Visualization of Blockchains by Nam Chu Hoai, January 2018

TypeScript

Naivecoin: a tutorial for building a cryptocurrency by Lauri Hartikka, (Source)

Java

Creating Your First Blockchain with Java, Part 1 by Kass, December 2017, (Source)

Kotlin

Let's implement a cryptocurrency in Kotlin by Vasily Fomin, July 2018, (Source)

SQL

Blockchain by Example in SQL Server by Benjamin Campbell, December 2017, (Source)

Rust

Building Blockchain in Rust Series by Jacob Lindahl, GeekLaunch, (Source), (Slide Decks in PDF)

Go

Building Blockchain in Go Series by Ivan Kuznetsov, (Source)

Blockchain Series in Go by by Coral Health (Source)

Talk Notes

More

See Build your own Blockchain / Cryptocurrency @ Build your own (insert technology here)

Samples

Blockchain from Scratch - Ruby Version

class Block

  attr_reader :timestamp
  attr_reader :data
  attr_reader :previous_hash
  attr_reader :hash

  def initialize(data, previous_hash)
    @timestamp     = Time.now
    @data          = data
    @previous_hash = previous_hash
    @hash          = calc_hash
  end

  def self.first( data="Genesis" )    # create genesis (big bang! first) block
    ## note: uses all zero for previous_hash ("0")
    Block.new( data, "0000000000000000000000000000000000000000000000000000000000000000" )
  end

  def self.next( previous, data="Transaction Data..." )
    Block.new( data, previous.hash )
  end

private

  def calc_hash
    sha = Digest::SHA256.new
    sha.update( @timestamp.to_s + @previous_hash + @data )
    sha.hexdigest
  end

end  # class Block


#####
## let's get started
##   build a blockchain a block at a time

b0 = Block.first( "Genesis" )
b1 = Block.next( b0, "Transaction Data..." )
b2 = Block.next( b1, "Transaction Data......" )
b3 = Block.next( b2, "More Transaction Data..." )

blockchain = [b0, b1, b2, b3]

pp blockchain

(Source: blockchain.rb)

will pretty print (pp) something like:

[#<Block:0x1eed2a0
  @timestamp     = 1637-09-15 20:52:38,
  @data          = "Genesis",
  @previous_hash = "0000000000000000000000000000000000000000000000000000000000000000",
  @hash          = "edbd4e11e69bc399a9ccd8faaea44fb27410fe8e3023bb9462450a0a9c4caa1b">,
 #<Block:0x1eec9a0
  @timestamp     = 1637-09-15 21:02:38,
  @data          = "Transaction Data...",
  @previous_hash = "edbd4e11e69bc399a9ccd8faaea44fb27410fe8e3023bb9462450a0a9c4caa1b",
  @hash          = "eb8ecbf6d5870763ae246e37539d82e37052cb32f88bb8c59971f9978e437743">,
 #<Block:0x1eec838
  @timestamp     = 1637-09-15 21:12:38,
  @data          = "Transaction Data......",
  @previous_hash = "eb8ecbf6d5870763ae246e37539d82e37052cb32f88bb8c59971f9978e437743",
  @hash          = "be50017ee4bbcb33844b3dc2b7c4e476d46569b5df5762d14ceba9355f0a85f4">,
 #<Block:0x1eec6d0
  @timestamp     = 1637-09-15 21:22:38,
  @data          = "More Transaction Data...",
  @previous_hash = "be50017ee4bbcb33844b3dc2b7c4e476d46569b5df5762d14ceba9355f0a85f4",
  @hash          = "5ee2981606328abfe0c3b1171440f0df746c1e1f8b3b56c351727f7da7ae5d8d">]

Comments from the reddit ruby posting:

Wait, so a blockchain is just a linked list?

No. A linked list is only required to have a reference to the previous element, a block must have an identifier depending on the previous block's identifier, meaning that you cannot replace a block without recomputing every single block that comes after. In this implementation that happens as the previous digest is input in the calc_hash method.

What about Proof of Work / Waste?

Let's add a proof of work / waste to the blockchain. In the classic blockchain you have to compute a block hash that starts with leading zeros (00). The more leading zeros the harder (more difficult) to compute. Let's keep it easy to compute with two leading zeros (00), that is, 16^2 = 256 possibilites (^1,2). Three leading zeros (000) would be 16^3 = 4_096 possibilites and four zeros (0000) would be 16^4 = 65_536 and so on.

(^1): 16 possibilties because it's a hex or hexadecimal or base 16 number, that is, 0 1 2 3 4 6 7 8 9 a (10) b (11) c (12) d (13) e (14) f (15).

(^2): A random secure hash algorithm needs on average 256 tries (might be lets say 305 tries, for example, because it's NOT a perfect statistic distribution of possibilities).

Example:

def compute_hash_with_proof_of_work( difficulty="00" )
  nonce = 0
  loop do
    hash = calc_hash_with_nonce( nonce )
    if hash.start_with?( difficulty )  
      return [nonce,hash]     ## bingo! proof of work if hash starts with leading zeros (00)
    else
      nonce += 1              ## keep trying (and trying and trying)
    end
  end
end

def calc_hash_with_nonce( nonce=0 )
  sha = Digest::SHA256.new
  sha.update( nonce.to_s + @timestamp.to_s + @previous_hash + @data )
  sha.hexdigest
end

(Source: blockchain_with_proof_of_work.rb)

Let's rerun the sample with the proof of work machinery added. Now the sample will pretty print (pp) something like:

[#<Block:0x1e204f0
  @timestamp     = 1637-09-20 20:13:38,
  @data          = "Genesis",
  @previous_hash = "0000000000000000000000000000000000000000000000000000000000000000",
  @nonce         = 242,
  @hash          = "00b8e77e27378f9aa0afbcea3a2882bb62f6663771dee053364beb1887e18bcf">,
 #<Block:0x1e56e20
  @timestamp     = 1637-09-20 20:23:38,
  @data          = "Transaction Data...",
  @previous_hash = "00b8e77e27378f9aa0afbcea3a2882bb62f6663771dee053364beb1887e18bcf",
  @nonce         = 46,
  @hash          = "00aae8d2e9387e13c71b33f8cd205d336ac250d2828011f5970062912985a9af">,
 #<Block:0x1e2bd58
  @timestamp     = 1637-09-20 20:33:38,
  @data          = "Transaction Data......",
  @previous_hash = "00aae8d2e9387e13c71b33f8cd205d336ac250d2828011f5970062912985a9af",
  @nonce         = 350,
  @hash          = "00ea45e0f4683c3bec4364f349ee2b6816be0c9fd95cfd5ffcc6ed572c62f190">,
 #<Block:0x1fa8338
  @timestamp     = 1637-09-20 20:43:38,
  @data          = "More Transaction Data...",
  @previous_hash = "00ea45e0f4683c3bec4364f349ee2b6816be0c9fd95cfd5ffcc6ed572c62f190",
  @nonce         = 59,
  @hash          = "00436f0fca677652963e904ce4c624606a255946b921132d5b1f70f7d86c4ab8">]

See the difference? All hashes now start with leading zeros (00) and the nonce is the random "lucky number" that makes it happen. That's the magic behind the proof of work.

Blockchain from Scratch - JavaScript Version

class Block {

  constructor(data, previousHash) {
    this.timestamp    = new Date()
    this.data         = data
    this.previousHash = previousHash
    this.hash         = this.calcHash()
  }

  calcHash() {
    var sha = SHA256.create()
    sha.update( this.timestamp.toString() + this.previousHash + this.data )
    return sha.hex()
  }

  static first( data="Genesis" ) {    // create genesis (big bang! first) block
    // uses all-zero previousHash
    return new Block( data, "0000000000000000000000000000000000000000000000000000000000000000" )
  }

  static next( previous, data="Transaction Data..." ) {
    return new Block( data, previous.hash )
  }
}


//////
// let's get started
//   build a blockchain a block at a time

b0 = Block.first( "Genesis" )
b1 = Block.next( b0, "Transaction Data..." )
b2 = Block.next( b1, "Transaction Data......" )
b3 = Block.next( b2, "More Transaction Data..." )


blockchain = [b0, b1, b2, b3]

console.log( blockchain )

(Source: blockchain.js)

will log something like:

[ Block {
     timestamp    : 1637-09-18 08:25:54,
     data         : 'Genesis',
     previousHash : '0000000000000000000000000000000000000000000000000000000000000000',
     hash         : 'c396de4c03ddb5275661982adc75ce5fc5905d2a2457d1266c74436c1f3c50f1' },
   Block {
     timestamp    : 1637-09-18 08:35:54,
     data         : 'Transaction Data...',
     previousHash : 'c396de4c03ddb5275661982adc75ce5fc5905d2a2457d1266c74436c1f3c50f1',
     hash         : '493131e09c069645c82795c96e4715cea0f5558be514b5096d853a5b9899154a' },
   Block {
     timestamp    : 1637-09-18 08:45:54,
     data         : 'Transaction Data......',
     previousHash : '493131e09c069645c82795c96e4715cea0f5558be514b5096d853a5b9899154a',
     hash         : '97aa3cb5052615d60ff8e6b41bef606562588c4874f011970ac2f218e2f0f4a8' },
   Block {
     timestamp    : 1637-09-18 08:55:54,
     data         : 'More Transaction Data...',
     previousHash : '97aa3cb5052615d60ff8e6b41bef606562588c4874f011970ac2f218e2f0f4a8',
     hash         : 'e10e020f832e46c2b60e1c3c0412bd370b2fde5f0f782c16eb87d0313ea0d3a3' } ]

Blockchain Articles

Reflections on the Blockchain by Rufus Pollock (Open Knowledge Foundation), July 2016 -- The DAO: Code is not Law – and It’s Dangerous to Think So ++ The Internet changed the world - surely the Blockchain will too? ++ Gold-rush or Internet-rush? ++ Governance Matters in Bitcoin ++ The Myth of a Costless, Ownerless Network ++ Lessons from History

On the Dangers of a Blockchain Monoculture by Tony Arcieri, January 2016 -- The Bitcoin blockchain: the world's worst database ++ Next-generation protocols ++ Decentralized ledger protocols ++ Bitcoin-NG ++ Blockchain! Blockchain! Blockchain! ++ The great decentralized database in the sky

I Don’t Believe in Blockchain by Tim Bray, May 2017

Minimum Viable Blockchain by Ilya Grigorik, May 2014 -- Securing transactions with triple-entry bookkeeping ++ Securing transactions with PKI ++ Balance = Σ(receipts) ++ Multi-party transfers & verification ++ Double-spending and distributed consensus - Requirements for a distributed consensus network; Protecting the network from Sybil attacks; Proof-of-work as a participation requirement ++ Building the minimum viable blockchain - Adding "blocks" & transaction fee incentives; Racing to claim the transaction fees; Resolving chain conflicts; Blocks are never final ++ Properties of the (minimum viable) blockchain

Blockchains by analogies and applications: How blockchain compares to Git, Raft, and other technologies. by Kieren James-Lubin, January 2016 -- Blockchains are databases ++ Understanding transactions ++ Persistent, replicated databases (related technology: Git) ++ Peer-to-peer networks (related technology: BitTorrent) ++ Distributed consensus (related technology: distributed databases, Raft) ++ Minting new coins (mining) ++ Embedded identities (related technology: TLS) ++ Smart contracts: Like SQL expressions & triggers ++ What can we really do with blockchains?

Blockchain Books

Attack of the 50 Foot Blockchain: Bitcoin, Blockchain, Ethereum & Smart Contracts by David Gerard, London, 2017 -- What is a bitcoin? ++ The Bitcoin ideology ++ The incredible promises of Bitcoin! ++ Early Bitcoin: the rise to the first bubble ++ How Bitcoin mining centralised ++ Who is Satoshi Nakamoto? ++ Spending bitcoins in 2017 ++ Trading bitcoins in 2017: the second crypto bubble ++ Altcoins ++ Smart contracts, stupid humans ++ Business bafflegab, but on the Blockchain ++ Case study: Why you can’t put the music industry on a blockchain

Mastering Bitcoin - Programming the Open Blockchain 2nd Edition, by Andreas M. Antonopoulos, 2017 - FREE (Online Source Version) -- What Is Bitcoin? ++ How Bitcoin Works ++ Bitcoin Core: The Reference Implementation ++ Keys, Addresses ++ Wallets ++ Transactions ++ Advanced Transactions and Scripting ++ The Bitcoin Network ++ The Blockchain ++ Mining and Consensus ++ Bitcoin Security ++ Blockchain Applications


BEWARE: Bitcoin is a gigantic ponzi scheme¹. To the moon!? The new gold standard!? Do NOT "invest" trying to get-rich-quick HODLing. Why not? The bitcoin code is archaic and out-of-date. Burn, baby, burn! Proof-of-work / waste is a global energy environmental disaster using 300 kW/h per bitcoin transaction (!) that's about 179 kilograms of CO₂ emissions². Programmable money (or the internet of value) for all future generations with (bitcoin) script without loops and jumps (gotos) and all "stateless"!? LOL.

¹: (Source: Best of Bitcoin Maximalist - Scammers, Morons, Clowns, Shills & BagHODLers - Inside The New New Crypto Ponzi Economics)

²: Assuming let's say 0.596 kilograms of CO₂ per kW/h (that's the energy efficiency in Germany) that's about 179 kilograms of CO₂ per bitcoin transaction (300 kW/h × 0.596 kg). For more insights see the Bitcoin Energy Consumption Index.


Programming Bitcoin from Scratch by Jimmy Song, 2019 - FREE (Online Source Version) -- Chapter 6 - Script - How Script Works • Example Operations • Parsing the Script Fields • Combining the Script Fields • Standard Scripts • p2pk • Problems with p2pk • Solving the Problems with p2pkh • Scripts Can Be Arbitrarily Constructed • Conclusion ++ Chapter 8 - Pay-to-Script Hash - Bare Multisig • Coding OP_CHECKMULTISIG • Problems with Bare Multisig • Pay-to-Script-Hash (p2sh) • Coding p2sh • Conclusion ++ Chapter 13 - Segregated Witness - Pay-to-Witness-Pubkey-Hash (p2wpkh) • p2wpkh Transactions • p2sh-p2wpkh • Coding p2wpkh and p2sh-p2wpkh • Pay-to-Witness-Script-Hash (p2wsh) • p2sh-p2wsh • Coding p2wsh and p2sh-p2wsh • Other Improvements • Conclusion

Programming Bitcoin Script Transaction (Crypto) Contracts Step-by-Step ( Beta / Rough Draft ) by Gerald Bauer et al, 2019 - FREE (Online Version) -- Let's start with building your own bitcoin stack machine from zero / scratch and let's run your own bitcoin ops (operations)...

Programming Blockchains in Ruby from Scratch Step-by-Step Starting w/ Crypto Hashes... ( Beta / Rough Draft ) by Gerald Bauer et al, 2018 - FREE (Online Version) -- (Crypto) Hash ++ (Crypto) Block ++ (Crypto) Block with Proof-of-Work ++ Blockchain! Blockchain! Blockchain! ++ Blockchain Broken? ++ Timestamping ++ Mining, Mining, Mining - What's Your Hash Rate? ++ Bitcoin, Bitcoin, Bitcoin ++ (Crypto) Block with Transactions (Tx)

Mastering Ethereum - Building Contract Services and Decentralized Apps on the Blockchain - by Andreas M. Antonopoulos, Gavin Wood, 2018 - FREE (Online Source Version) What is Ethereum ++ Introduction ++ Ethereum Clients ++ Ethereum Testnets ++ Keys and Addresses ++ Wallets ++ Transactions ++ Contract Services ++ Tokens ++ Oracles ++ Accounting & Gas ++ EVM (Ethereum Virtual Machine) ++
Consensus ++
DevP2P (Peer-To-Peer) Protocol ++ Dev Tools and Frameworks ++ Decentralized Apps ++ Ethereum Standards (EIPs/ERCs)

Building Decentralized Apps on the Ethereum Blockchain by Roberto Infante, 2018 - FREE chapter 1 -- Understanding decentralized applications ++ The Ethereum blockchain ++ Building contract services in (JavaScript-like) Solidity ++ Running contract services on the Ethereum blockchain ++ Developing Ethereum Decentralized apps with Truffle ++ Best design and security practice

Programming Crypto Blockchain Contracts Step-by-Step Book / Guide ( Beta / Rough Draft ) by Gerald Bauer et al, 2019 - FREE (Online Version) -- Let's Start with Ponzi & Pyramid Schemes. Run Your Own Lotteries, Gambling Casinos and more on the Blockchain World Computer...

Programming Cryptocurrencies and Blockchains in Ruby ( Beta / Rough Draft ) by Gerald Bauer et al, 2018 - FREE (Online Version) @ Yuki & Moto Press Bookshelf -- Digital $$$ Alchemy - What's a Blockchain? - How-To Turn Digital Bits Into $$$ or €€€? • Decentralize Payments. Decentralize Transactions. Decentralize Blockchains. • The Proof of the Pudding is ... The Bitcoin (BTC) Blockchain(s) ++ Building Blockchains from Scratch - A Blockchain in Ruby in 20 Lines! A Blockchain is a Data Structure • What about Proof-of-Work? What about Consensus? • Find the Lucky Number - Nonce == Number Used Once ++ Adding Transactions - The World's Worst Database - Bitcoin Blockchain Mining • Tulips on the Blockchain! Adding Transactions ++ Blockchain Lite - Basic Blocks • Proof-of-Work Blocks • Transactions ++ Merkle Tree - Build Your Own Crypto Hash Trees; Grow Your Own Money on Trees • What's a Merkle Tree? • Transactions ++ Central Bank - Run Your Own Federated Central Bank Nodes on the Blockchain Peer-to-Peer over HTTP • Inside Mining - Printing Cryptos, Cryptos, Cryptos on the Blockchain ++ Awesome Crypto ++ Case Studies - Dutch Gulden • Shilling • CryptoKitties (and CryptoCopycats)

Blockchain for Dummies, IBM Limited Edition by Manav Gupta, 2017 - FREE (Digital Download w/ Email) -- Grasping Blockchain Fundamentals ++ Taking a Look at How Blockchain Works ++ Propelling Business with Blockchains ++ Blockchain in Action: Use Cases ++ Hyperledger, a Linux Foundation Project ++ Ten Steps to Your First Blockchain application

Get Rich Quick "Business Blockchain" Bible - The Secrets of Free Easy Money, 2018 - FREE -- Step 1: Sell hot air. How? ++ Step 2: Pump up your tokens. How? ++ Step 3: Revolutionize the World. How?

Best of Bitcoin Maximalist - Scammers, Morons, Clowns, Shills & BagHODLers - Inside The New New Crypto Ponzi Economics by Trolly McTrollface, et al, 2018 - FREE

Crypto Facts - Decentralize Payments - Efficient, Low Cost, Fair, Clean - True or False? by Nouriel Roubini, David Gerard, et al, 2018 - FREE

Crypto is the Mother of All Scams and (Now Busted) Bubbles - While Blockchain Is The Most Over-Hyped Technology Ever, No Better than a Spreadsheet/Database by Nouriel Roubini, 2018 - FREE

IslandCoin White Paper - A Pen and Paper Cash System - How to Run a Blockchain on a Deserted Island by Tal Kol -- Motivation ++ Consensus ++ Transaction and Block Specification - Transaction format • Block format • Genesis block ++ References

Blockchain (Lite) Crypto Hash Libraries

RubyJavaScript

Ruby

blockchain.lite (github: openblockchains/blockchain.lite.rb, gem: blockchain-lite) - build your own blockchain with crypto hashes - revolutionize the world with blockchains, blockchains, blockchains one block at a time

require 'blockchain-lite'

b0 = Block.first( "Genesis" )
b1 = Block.next( b0, "Transaction Data..." )
b2 = Block.next( b1, "Transaction Data......" )
b3 = Block.next( b2, "More Transaction Data..." )

blockchain = [b0, b1, b2, b3]

pp blockchain   

will pretty print (pp) something like:

[#<Block:0x1eed2a0
  @timestamp     = 1637-09-15 20:52:38,
  @data          = "Genesis",
  @previous_hash = "0000000000000000000000000000000000000000000000000000000000000000",
  @hash          = "edbd4e11e69bc399a9ccd8faaea44fb27410fe8e3023bb9462450a0a9c4caa1b">,
 #<Block:0x1eec9a0
  @timestamp     = 1637-09-15 21:02:38,
  @data          = "Transaction Data...",
  @hash          = "eb8ecbf6d5870763ae246e37539d82e37052cb32f88bb8c59971f9978e437743",
  @previous_hash = "edbd4e11e69bc399a9ccd8faaea44fb27410fe8e3023bb9462450a0a9c4caa1b">,
  ...

JavaScript

blockchain.lite (github: openblockchains/blockchain.lite.js, npm: blockchain-lite) - build your own blockchain with crypto hashes - revolutionize the world with blockchains, blockchains, blockchains one block at a time

const Blocks = require( "blockchain-lite" )

// use basic block
let Block = Blocks.basic

let b0 = Block.first( 'Genesis' )
let b1 = Block.next( b0, 'Transaction Data...' )
let b2 = Block.next( b1, 'Transaction Data......' )
let b3 = Block.next( b2, 'More Transaction Data...' )

let blockchain = [b0, b1, b2, b3]

console.log( blockchain )

will log something like:

[ Block {
    timestamp:     2017-09-25 17:03:38,
    data:         'Genesis',
    previousHash: '0000000000000000000000000000000000000000000000000000000000000000',
    hash:         '08f4fa71628c5bc6b430228738bc8c41afaf508ece0b1cf9c9cac53d02e11829' },
  Block {
    timestamp:     2017-09-25 17:13:38,
    data:         'Transaction Data...',
    previousHash: '08f4fa71628c5bc6b430228738bc8c41afaf508ece0b1cf9c9cac53d02e11829',
    hash:         '740a4aeb3441484c96d1e7f63d31b716220ccee3b6fe94547cae2afbb6010626' },
  Block {
    timestamp:     2017-09-25 17:23:38,
    data:         'Transaction Data......',
    previousHash: '740a4aeb3441484c96d1e7f63d31b716220ccee3b6fe94547cae2afbb6010626',
    hash:         '28b6892a069e2ff7f1c3128ab495d7cd9b9b1636a51a7f69db93a14b1ee6b1a7' },
  Block {
    timestamp:     2017-09-25 17:33:38,
    data:         'More Transaction Data...',
    previousHash: '28b6892a069e2ff7f1c3128ab495d7cd9b9b1636a51a7f69db93a14b1ee6b1a7',
    hash:         '4cc0329b2c0cb32e0451fa3179bd944d4cd0fcf410939172f979e9fd2aa9f5f3' } ]

Git, Git, Git - The Stupid Content Tracker with Crypto Hashes

Everything is local. Distributed is the new centralized.

Quotes - Blockchains and Git

Yep, that's the joke. Nobody has been able to explain to me how the "blockchain" buzzword is significantly different to "git repo". -- Yaakov

But if you said "let's build a currency where all transactions are stored in a git repo" you wouldn't be taken seriously for even 24 hrs. -- Yaakov

Soon explaining git like "a git repo is like a blockchain with commits instead of blocks". -- Nicolás Berger

"A local branch is like a state channel. It can be pushed and merged into the master blockchain at any moment." -- Nicolás Berger

The #Blockchain has changed the world. Here I make the argument that the #Blockchain is just like #git. -- Jackson Kelley

git merge [-m REF] [-g BLOB] --push Merge and push all signed commits to the blockchain. -- Git Commands

Books

Learn Enough Git to Be Dangerous by Michael Hartl - FREE (Online Version) -- Getting started ++ Backing up and sharing ++ Intermediate workflow ++ Collaborating ++ Conclusion ++ Advanced setup

Pro Git by Scott Chacon and Ben Straub, 2nd Edition, 2014 - FREE (Online Version) -- Getting Started ++ Git Basics ++ Git Branching ++ Git on the Server ++ Distributed Git ++ GitHub ++ Git Tools ++ Customizing Git ++ Git and Other Systems ++ Git Internals ++ A1: Git in Other Environments ++ A2: Embedding Git in your Applications ++ A3: Git Commands

Git gets easier once you get the basic idea that branches are homeomorphic endofunctors mapping submanifolds of a Hilbert space. -- Anonymous

Open Distributed Databases on Git

football.db - open public domain football datasets (incl. clubs, national teams, leagues, match schedules, etc.)

world.db - open public domain world (country) datasets

beer.db - open public domain beer & brewery datasets

Add a beer transaction to the #blockchain on #git and win a free Wiener Lager beer! Cheers. Prost. -- Gerald Bauer @ Austria Codes

Open Distributed (Hyper) Ledger Books on Git

Shilling (or Schilling) - Shilling on the Blockchain! - Rock-Solid Alpine Dollar from Austria

Tulips - Tulips on the Blockchain! - Learn by Example from the Real World (Anno 1637) - Buy! Sell! Hold! Enjoy the Beauty of Admiral of Admirals, Semper Augustus, and More

Classic Tulip Mania

A period in the Dutch Golden Age during which contract prices for bulbs of the recently introduced tulip reached extraordinarily high levels and then dramatically collapsed in February 1637.

Quotes - Blockchains are the next Internets / Tulips

People who compare digital tokens to tulips are essentially saying digital tokens are a bubble backed by nothing but pure hype and speculation.

What they fail to understand is that tulips come from dirt, not a blockchain.

And as we all know, blockchain is possibly the best technological innovation since the internet. It will have a tremendous impact on global business and society in general. -- TulipToken

Books

Tulipomania: The Story of the World's Most Coveted Flower & the Extraordinary Passions It Aroused by Mike Dash, 2001 -- A Mania for Tulips ++ The Valley of Tien Shan ++ Within the Abode of Bliss ++ Stranger from the East ++ Clusius ++ Leiden ++ An Adornment to the Cleavage ++ The Tulip in the Mirror ++ Florists ++ Boom ++ At the Sign of the Golden Grape ++ The Orphans of Wouter Winkel ++ Bust ++ Goddess of Whores ++ At the Court of the Tulip King ++ Late Flowering

Tulipmania: Money, Honor, and Knowledge in the Dutch Golden Age by Anne Goldgar, 2007 -- Something Strange ++ Art & Flowers ++ Bloemisten ++ Grieving Money ++ Bad Faith ++ Cabbage Fever ++ Glossary ++ A Note on Money

Breaking News: CryptoKitties (Yes, Cute Little Cartoon Cats) on the Blockchain!

Collectible. Breedable. Adorable.

Collect and breed digital cats. Start meow. Buy! Sell! Hold!

Learn more @ cryptokitties.co

Latest (and Greatest) Investment Opportunity!

Blockchain has unlocked the magic of digital scarcity, and combining that with the power of making the digital goods persistent gives them a potential value that is only limited by how much prestige a wealthy person might place on ownership of the item.

-- Justin Poirier

All I want for Christmas is a CryptoKitty.

-- Kayla Williams

I got a fever. And the only prescription is more CryptoKitties.

-- Eduardo Salazar

My Gen 7 CryptoKitty #104375. The Future is Meow.

-- Anshul Dhawan

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  • UNIQUE Virgin Peach Googly Gold Mauveover gen:2 cooldown:1 0.87992% RARE
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  • I'm giving away a Gen 1 FAST Gold for free...

-- CrypoKittiesMarket

Awesome CryptoKitties (and CryptoCopycats)

A collection about Awesome CryptoKitties (Yes, Cute Little Cartoon Cats) on the Blockchain! and CryptoCopycats - digital collectibles secured on a distributed public databases w/ crypto hashes. Are CryptoPuppies the new CryptoKitties? Learn by Example from the Real World (Anno 2017) - Buy! Sell! Hodl!

More @ cryptocopycats/awesome-cryptokitties

Events, Meetups, Orgs

Revolutionize the world one country at a time. Blockchainers of the world, unite!

Awesome Awesomeness

A curated list of awesome lists.

  • Blockchain Stuff -- a curated list of blockchain and general cryptocurrency resources
  • Awesome Blockchain by Igor Barinov et al -- a curated list of the bitcoin blockchain services
  • Awesome Blockchain by Tim Reznich et al -- a curated list of blockchain services and exchanges
  • Awesome Blockchain by istinspring et al -- a curated list of awesome projects and services based on blockchain technology
  • Awesome Coins by Kenneth Reitz et al -- a guide to crypto-currencies and their algos
  • Awesome CryptoKitties (and CryptoCopycats) by Gerald Bauer et al -- a curated list about the awesome crypto kitties and copycats
  • Awesome Git by Dick Tang et al -- a curated list of amazingly awesome Git tools, resources and shiny things
  • Awesome by Sindre Sorhus et al -- a curated list of awesome lists

Author: openblockchains
Source Code: https://github.com/openblockchains/awesome-blockchains
License: CC0-1.0 License

#blockchain 

Devin Pinto

1606971339

Certified Blockchain Expert™ | Blockchain Certification | Blockchain Council

A multitude of use cases around the numerous industrial segments are now contained in the blockchain technology that once began as the underlying system for Bitcoin trading. One of the main impacts on the financial sector has been felt. Blockchain technology has been publicly adopted by businesses like JP Morgan. The financial sector is suffering from data protection problems, faster transactions, transparency and other bottlenecks that hamper the growth of businesses that rely on monetary transactions from banks and NBFCs. Blockchain could therefore be a possible solution here. Banks and financial sectors can easily solve the disadvantages that hold back the banks’ smooth functioning with Blockchain’s involvement.

Some of the biggest developments we have seen in the Blockchain sector are the development of Blockchain platforms such as Hyperledger Sawtooth, Hyperledger Fabric, Corda, etc This approved Blockchain not only ensures that the system operates efficiently, but also ensures that transactions take place at a faster rate. It actually helps the banking system work much better and in a more effective way.

How the financial sector is impacted by Blockchain:

1. Providing a safe platform-
The need for a secured platform is one of the greatest challenges facing most banking and financial institutions. As most of the transactions and other work have now been digitised, most banks and other allied companies are looking for a stable platform that is free of any mistakes or defects. In addition, there is also a high rise in the need for a network that can efficiently combat data breach problems, and so we have Blockchain. By time-stamping all information or data on it this DLT platform works. This guarantees full security. And with the introduction of approved Blockchain networks, the security feature is even more assured.

2. No third party- Time lag and paperwork are two weaknesses of the financial sector that appear to hold up the processes and ultimately influence the company’s efficiency as well. We can solve these problems with the assistance of Blockchain technology and thus ensure quicker transactions. Blockchain technology operates on peer-to-peer transactions, ensuring that for authentication and approval, there is no need to rely on a third party, which speeds up the transaction process.

3. Tracking and tracing- For banking firms, these features can be highly beneficial. Banks invest a large amount of money on authentication and verification, amid all the efforts of false identity cases, and fraud reports are growing, we can easily put an end to it with Blockchain. As data tracking and tracing becomes simpler and history can be easily traced back, compared to the traditional technologies that banks use, it becomes easier to rely on this platform.

These are the three big benefits that Blockchain can reap from the banking and financial field. Blockchain developers and Blockchain experts are in high demand because of this, and we will see an increase in this number in the times to come.

Conclusion- The Blockchain Council provides Blockchain with the best online certificate programme. This detailed curriculum will allow you to absorb all Blockchain-related knowledge while also learning how to incorporate it. Then what are you going to wait for? Register for today’s Blockchain certification.

#blockchain technology #blockchain development #blockchain expert #blockchain professional #blockchain developer

Ajay Kapoor

1623918965

Custom Blockchain Development & Outsourcing Company India

Being one of leading blockchain development companies in India, we have marked a niche by providing some successful Blockchain based software solutions on ethereum, hyperledger, Smart Contracts, and much more. You can leverage Blockchain technology to enhance data security, complete process automation, reduce data storage cost, eliminates duplication of data and reduce time,

We have industry best experts to provide you feature packed Blockchain development services catering to your business challanges. Get in touch now to explore the benefits of Blockchain for your business!

#blockchain-development-company-in-india #blockchain #blockchain-companies-india #blockchain-outsourcing-companies #blockchain-development-services #blockchain-development-company