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Bitcoin Proof of Work (PoW)

Definition: The Bitcoin proof of work is the underlying consensus algorithm for the bitcoin blockchain network. It aims to find a combination of predefined inputs which result in a hash value lower than a certain target threshold.

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Hash Functions – Overview & Explanation

Definition: A hash function is a function which takes a value of arbitrary length as input (preimage) and calculates an output (digest) of fixed length.

In this post we explain what hash functions are and how they work.

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History Ethereum

History / Development of Ethereum

This post provides a collection of material dealing with the history and technical development of Ethereum.

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Verifiable Random Number

Decentralized Verifiable Random Functions (VRN)

VRN = Verifiable Random Number

A VRN is a function that creates a random number in decentralized fashion. The Outcome of this function can be verified by thirdparties. This is important to confirmt that the resulting number is truely (pseudo)random.

Properties of VRN

Desired properties of a VRNs are:

  • Availability/ Livelines
  • Quantum Resistence
  • Verifiability
  • Unbiased
  • Unpredictability
  • Scaleability

Material / Ressources for Verifiable Random Functions (VRN)

Overview Ressources

XOR, Commit Verify, RANDAO, Hash Onions, Pedersens Scheme

  • Explains a solution to the last actor problem by using a threshold scheme from 6:15
  • BLS Threshold Signatures
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Blockchain in the public sector – practical guide by comptia

This article gives a comprehensive overview about the basics of blockchain and distributed ledger technologies in a highlevel way. It offers links to some reports and surveys regarding the adoption of blockchain and its outlook for the future.

During this report several use cases are touched and it is highlighted that many US authorities have experimented with blockchain and dlt so far.

Beside the description of use cases and adoptions the report provides policy recommendations like defined standards and interoperability, standardized market places as well as “sand boxes” for testing this new technology.

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ECON Committee on Virtual Currencies and Central Banks

This paper describes the challenges for central banks arising by virtual currencies (VC) like Bitcoin.

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Consequences of forking a token

This step by step guide explains how to fork a token on a ethereum smart contract.

Forking a token means, simply copying the source code and the values (amount of token held by each address). The question however is how to get all details from the contract.

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List of attacks on smart contracts

Security is a major concern for smart contracts. This source lists many known attack vectors to Solidity smart contracts. It is valuable for developers and auditors alike.

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Sign and verify Signature with Solidity and Javascript

Tutorial about signing and validating data in solidity and javascript.

Creating and validating signatures is crucial part in many transactions and applications.

In this tutorial the signature is created in javascript utilizing the libraries eth-crypto, web3 and ganache-cli.

The javascript library EthCrypto ist responsible for signing the message (for example with a keccak256).

The validation takes place in a smart contract (Solidity).

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Validating a signature in Solidity.

Validating a  signature in Solidity. This smart contract written in Solidity shows how to validate a signature passed to a function.