On February 16, 2018, Coinbase admitted that some customers were overcharged in error for credit and debit purchases of cryptocurrencies. The problem was initiated when banks and card issuers changed the merchant category code (MCC) for cryptocurrency purchases earlier this month. This meant that cryptocurrency payments would now be processed as "cash advances", meaning that banks and credit card issuers could begin charging customers cash-advance fees for cryptocurrency purchases. Any customers who purchased cryptocurrency on their exchange between January 22 and February 11, 2018 could have been affected. At first, Visa blamed Coinbase, telling the Financial Times on February 16 that it had "not made any systems changes that would result in the duplicate transactions cardholders are reporting." However, the latest statement from Visa and Worldpay on the Coinbase blog clarifies: "This issue was not caused by Coinbase."[45]
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. 
For those of you who have not been paying attention to one of the biggest trends in investing and tech, cryptocurrencies are digital currencies using encryption techniques that regulate the generation of currency and verify the transfer of funds, operating independently of a central bank. Units of currency are created through a process referred to as mining.
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是Blockchain仅用于Cryptocurrency


         其原理是:假设两个使用IP协议的站点A、B通过第三层交换机进行通信,发送站点A在开始发送时,把自己的IP地址与B站的IP地址比较,判断B站是否与自己在同一子网内。若目的站B与发送站A在同一子网内,则进行二层的转发。若两个站点不在同一子网内,如发送站A要与目的站B通信,发送站A要向“缺省网关”发出ARP(地址解析)封包,而“缺省网关”的IP地址其实是三层交换机的三层交换模块。当发送站A对“缺省网关”的IP地址广播出一个ARP请求时,如果三层交换模块在以前的通信过程中已经知道B站的MAC地址,则向发送站A回复B的MAC地址。否则三层交换模块根据路由信息向B站广播一个ARP请求,B站得到此ARP请求后向三层交换模块回复其MAC地址,三层交换模块保存此地址并回复给发送站A,同时将B站的MAC地址发送到二层交换引擎的MAC地址表中。从这以后,当A向B发送的数据包便全部交给二层交换处理,信息得以高速交换。由于仅仅在路由过程中才需要三层处理,绝大部分数据都通过二层交换转发,因此三层交换机的速度很快,接近二层交换机的速度,同时比相同路由器的价格低很多。

cryptocurrency卡


从广义上来看,网络交换机分为两种:广域网交换机和局域网交换机。广域网交换机主要应用于电信领域,提供通信用的基础平台。而局域网交换机则应用于局域网络,用于连接终端设备,如PC机及网络打印机等。从传输介质和传输速度上可分为以太网交换机、快速以太网交换机、千兆以太网交换机、FDDI交换机、ATM交换机和令牌环交换机等。从规模应用上又可分为企业级交换机、部门级交换机和工作组交换机等。各厂商划分的尺度并不是完全一致的,一般来讲,企业级交换机都是机架式,部门级交换机可以是机架式(插槽数较少),也可以是固定配置式,而工作组级交换机为固定配置式(功能较为简单)。另一方面,从应用的规模来看,作为骨干交换机时,支持500个信息点以上大型企业应用的交换机为企业级交换机,支持300个信息点以下中型企业的交换机为部门级交换机,而支持100个信息点以内的交换机为工作组级交换机。 [3] 

什么是基于Cryptocurrency


Bitcoin (BTC) is the world’s first decentralized digital currency and payment system and is by far the most known and valuable cryptocurrency. It was created in 2009 by an anonymous person or group called Satoshi Nakamoto. Bitcoin enables transactions to be sent peer-to-peer without passing through a central authority. The transactions are recorded on a decentralized public ledger called the blockchain and each payment acquires a small transaction fee to cover the cost of the network. The total supply of Bitcoin is 21 million and it’s smallest unit of bitcoin is called a Satoshi, it’s a hundred millionth of a bitcoin – 0.00000001 BTC. The creation of Bitcoin’s is happening through mining. Miners have the task to validate transactions and keep the network secure. Their efforts are rewarded by new minted Bitcoins and transactions fees. Bitcoin can be exchanged for fiat or other cryptocurrencies, products and services. Over 100,000 merchants and vendors accepts bitcoin as a payment.

你可以买到Zcash上Coinbase


In February 2019, Coinbase announced that it had acquired "blockchain intelligence platform" Neutrino, an Italy-based startup, for an undisclosed price.[33] The acquisition raised concern among some Coinbase users[34] based on Neutrino founders' connection to the Hacking Team, which has been accused of providing internet surveillance technology to governments with poor human rights records.[35] On March 4, 2019, Coinbase CEO Brian Armstrong said his company "did not properly evaluate" the deal from a due diligence perspective and thus any Neutrino staff who previously worked at Hacking Team "will transition out of Coinbase."[36]
In August 2019, Coinbase announced that it was targeted by a sophisticated hacking attack attempt in mid-June. This reported attack used spear-phishing and social engineering tactics (including sending fake e-mails from compromised email accounts and created a landing page at the University of Cambridge) and two Firefox browser zero-day vulnerabilities. One of the Firefox vulnerabilities could allow an attacker to escalate privileges from JavaScript on a browser page (CVE-2019–11707) and the second one could allow the attacker to escape the browser sandbox and execute code on the host computer (CVE-2019–11708). Coinbase's security team detected and blocked the attack, the network was not compromised, and no cryptocurrency was stolen.[39][40][41]

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