To realize digital cash you need a payment network with accounts, balances, and transaction. That‘s easy to understand. One major problem every payment network has to solve is to prevent the so-called double spending: to prevent that one entity spends the same amount twice. Usually, this is done by a central server who keeps record about the balances.
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In May 2018, Bitcoin Gold (and two other cryptocurrencies) were hit by a successful 51% hashing attack by an unknown actor, in which exchanges lost estimated $18m. In June 2018, Korean exchange Coinrail was hacked, losing US$37 million worth of altcoin. Fear surrounding the hack was blamed for a $42 billion cryptocurrency market selloff. On 9 July 2018 the exchange Bancor had $23.5 million in cryptocurrency stolen.
Despite the intricate technology associated with and necessary for cryptocurrency investing, speculation and possession, Coinbase has created an apparatus that makes this process remarkably easy and familiar, almost like buying and selling stocks. This screenshot from the Coinbase site shows real-time cryptocurrency prices and doesn't look too different from your ordinary online stock tracker.
比特币与莱特币都采用了区块链技术，且都有51%攻击的问题。它们采用区块链技术，所有历史记录按照时间先后顺序，打包成一个个单独的区块，再把这些单独的区块链接在一起形成一个总账本  。这些区块内除了包含交易记录外，还包含新发行的莱特币和交易的手续费，这两笔钱支付给挖矿的矿工作为酬劳。无论谁挖到该区块，那么该区块内含有的新发行的莱特币和交易的手续费这两笔钱都归挖到者，以鼓励矿工积极参与结算。区块链技术容易产生51%攻击的问题：无论任何组织甚至个人，只要掌控某一种基于区块链原理的虚拟货币的全部运算能力的51%，这个人或组织就能够任意操纵该虚拟货币的所有交易。如果区块链只认运算能力最大者，谁的运算能力最大，谁就能抢到下一个区块，如果某个个人或组织掌控了全部运算能力的51%，那就意味着没人比他运算能力更强，故而他就可以随意操纵。所以，对于基于区块链原理的虚拟货币，参与挖矿的越多就越健壮，运算能力越分散就越健壮；挖坑者越少越脆弱，运算能力越集中就越脆弱，矿池越集中也就越脆弱  。
Coinbase is a all around awesome platform to quickly and swiftly get into the world of crypto assets. Trusted them from day one and so far so good ! The only negative situation I have encountered has been 1 . I bought $25 dollars of bitcoin and was charged twice but only got $25 worth of bitcoin .... contacted coinbase and that very same day got a email back from them saying they knew about the situation and that they where on top of it because it happened to more people that week... a day or two pass and I received another email saying my problem was resolved..... it wasn’t and still hasn’t been resolved! Thank God I only bought $25 and not a lot more ! It’s $25 I’m not going to be after anyone for that little amount of money but it definitely impacted my good experience with coinbase and their over all standing with me , my friends and my family after this situation that has still not been resolved .
The novel hybrid consensus-based TrueChain tends to rely on POW consensus for random node selection, instead of using the slow chain mechanism to ensure security like Thunder.Although TrueChain has released dozens of Dapps, the number of its addresses (including active ones)and transactions is small. After the mainnet is launched, the project has run out of short-term bullish factors, which, plus the underdevelopment of its ecosystem, leads to a price slump within a short period of time. It will take some time for investors to regain confidence.
Homero Josh Garza, who founded the cryptocurrency startups GAW Miners and ZenMiner in 2014, acknowledged in a plea agreement that the companies were part of a pyramid scheme, and pleaded guilty to wire fraud in 2015. The U.S. Securities and Exchange Commission separately brought a civil enforcement action against Garza, who was eventually ordered to pay a judgment of $9.1 million plus $700,000 in interest. The SEC's complaint stated that Garza, through his companies, had fraudulently sold "investment contracts representing shares in the profits they claimed would be generated" from mining.
The validity of each cryptocurrency's coins is provided by a blockchain. A blockchain is a continuously growing list of records, called blocks, which are linked and secured using cryptography. Each block typically contains a hash pointer as a link to a previous block, a timestamp and transaction data. By design, blockchains are inherently resistant to modification of the data. It is "an open, distributed ledger that can record transactions between two parties efficiently and in a verifiable and permanent way". For use as a distributed ledger, a blockchain is typically managed by a peer-to-peer network collectively adhering to a protocol for validating new blocks. Once recorded, the data in any given block cannot be altered retroactively without the alteration of all subsequent blocks, which requires collusion of the network majority.
But while cryptocurrencies are more used for payment, its use as a means of speculation and a store of value dwarfs the payment aspects. Cryptocurrencies gave birth to an incredibly dynamic, fast-growing market for investors and speculators. Exchanges like Okcoin, Poloniex or shapeshift enables the trade of hundreds of cryptocurrencies. Their daily trade volume exceeds that of major European stock exchanges.
If you do have this much money tied up in Bitcoin, though, you may want a more secure space to store it. If this is the case, Coinbase offers a Coinbase vault, which has time-delayed withdrawals (giving you 48 hours to cancel a withdrawal) and the option of multiple approvers, increasing security by ensuring that all withdrawals are approved by multiple people. They also offer a multisig vault, which is basically an even more involved and more secure vault, requiring multiple keys to unlock.
In 2014, the company grew to one million users, acquired the blockchain explorer service Blockr and the web bookmarking company Kippt, secured insurance covering the value of bitcoin stored on their servers, and launched the vault system for secure bitcoin storage. Throughout 2014, the company also formed partnerships with Overstock, Dell, Expedia, Dish Network, and Time Inc. allowing those firms to accept bitcoin payments. The company also added bitcoin payment processing capabilities to the traditional payment companies Stripe, Braintree, and PayPal.
All of those factors make mining cryptocurrencies an extremely competitive arms race that rewards early adopters. However, depending on where you live, profits made from mining can be subject to taxation and Money Transmitting regulations. In the US, the FinCEN has issued a guidance, according to which mining of cryptocurrencies and exchanging them for flat currencies may be considered money transmitting. This means that miners might need to comply with special laws and regulations dealing with this type of activities.
Welcome to the 32nd Coin Report. In today’s report, I will be assessing the fundamental and technical strengths and weaknesses of ExchangeCoin. This will be comprised of an analysis of a number of significant metrics, an evaluation of the project’s community and development and an overview of its price-history. The report will conclude with a grading out of 10. ExchangeCoin was launched in November 2017 with an ICO that raised 650 BTC, equating to over $5,000,000 at the time. The token issued, EXCC, has a maximum supply of 32,003,133, with 4mn EXCC sold during the ICO. Further, the project also has a premine of 12.1mn EXCC, equating to 37.95% of the maximum supply (from which the 4mn was sold to the public in the token sale). The token itself operates on the Equihash algorithm, and underwent a hard fork in July 2018, after which the network migrated to a dual Proof-of-Work/Proof-of-Stake consensus mechanism, with 30% of block rewards rewarded to stakers and 70% to miners. The block reward is progressively diminishing, with the current reward at 24.5 EXCC per block, with 2.5-minute block times.