kraken safest crypto exchange

The crypto world has a hacking problem.

Specifically, cryptocurrency exchanges have a hacking problem. In 2018 alone, we’ve seen at least four major exchange hacks with more than $750 million stolen (not to mention a few smaller exchange hacks).

Security and protection from hackers have become paramount when using a crypto exchange, but how do you assess the security threat?

Luckily, a prominent cybersecurity firm, Group-IB, has done it for us. In a new report, published in partnership with CryptoIns, every major crypto exchange is ranked based on a variety of security features.

Kraken is the Most Secure Cryptocurrency Exchange

Founded in 2011, Kraken is one of the oldest crypto exchanges out there. In that time, they have developed one of the most impenetrable exchanges.

Kraken was the first exchange to pass a verified proof-of-reserves audit and is integrated with BitGo, one of the leading cryptocurrency security companies.

The Group-IB report cites Kraken as the most secure exchange as a result. Further, Kraken is the only name in the report’s top-tier group, considered the least risky.

Further reading: 8 Cryptocurrency Best Practices (Keep Your Crypto Safe)

The Four-Tier Ranking

Group-IB divides the major cryptocurrency exchanges into four groups based on their security features. Below are the results:

Group A – Kraken.

Group B – Bittrex, Coinbase Pro

Group C – Binance, Bitifinex, Bitmex, Bithumb, Poloniex, Localbitcoins, MyEtherWallet.

Group D – OKEx, Huobi Pro, Coincheck, Bitstamp, Bit-Z, Zaif

OKEx: “Completely Uninsurable”

Group-IB considered the last pool “completely uninsurable” due to the security risk involved. That should come as a warning sign to anyone trading or storing their cryptocurrencies on these exchanges.

Perhaps the most surprising name in this group is OKEx. The exchange is now the second-largest in the world by 24-hour volume and was named the “Crypto Exchange of the Year” at the recent Malta Blockchain Awards.

How Were the Crypto Exchanges Ranked?

Group-IB compiled the rankings based on a number of security features including:

  • Technical security levels.
  • The reliability of private key storage.
  • Password requirements and 2FA options.
  • Protection of customer data.
  • Risk management.
  • Know your customer (KYC) and anti-money laundering (AML) procedures.

The exchanges were also submitted to penetration testing and finally ranked according to the relative cost of insuring them.

The exact scores in each of the categories were not released publicly for confidentiality reasons.

Caution: Don’t Keep Your Money on an Exchange for Longer Than You Need To

These rankings are vital for anyone looking to buy or sell cryptocurrencies. However, it doesn’t change the fact that keeping your cryptocurrency on an exchange is incredibly risky.

Hackers deliberately target exchanges and, as you can see above, not all institutions are secure.

The best course of action is to keep your cryptocurrency off the exchange and in a cold-storage wallet (i.e. not connected to the internet).

Exchanges are great for buying, selling, and trading, but don’t keep store your money there for a long period of time. If you don’t have 100% control of your private keys, you don’t have 100% control of your crypto.

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51% attack cryptocurrency hacker

51% attacks. Merely mentioning them makes crypto traders a little fidgety, and with good reason. 

A successful 51% attack against a cryptocurrency would, at best, take a big chunk out of that cryptocurrency’s price. And, at worst, could end use of the cryptocurrency altogether. 

When you look at it that way, a 51% attack sounds terrifying. Let’s look at how they happen, and how blockchain projects keep them safe.

51% Attacks, Explained in Simple Terms

Put simply, a 51% attack could occur when a malicious actor (or group of actors) commands more than half the mining or hashing power on a blockchain.

As you can see in the chart below, many different mining pools are at work on the Bitcoin blockchain. If one of those pools reached a 51% majority, they could, hypothetically, initiate a 51% attack.

51% attack bitcoin mining pools
The proportional makeup of bitcoin miners of the network. Credit: CoinDance

But What Does a 51% Attack Do?

A 51% attack, also known as a “double-spend attack”, allows the attacker to rewrite history on a blockchain. 

In practical terms, it means the attacker can spend that particular cryptocurrency twice. 

As an attacker, I would buy something with bitcoin, then initiate a 51% attack to create a new version of the blockchain – one that doesn’t include my transaction.

Sounds pretty scary when you put it like that. That said, it is rather difficult to actually pull off a 51% attack on an established network. Bitcoin, for example, has never been hit by a 51% attack. Most large cryptocurrencies are safe, software bugs notwithstanding. 

And, even if you can pull one off, you only become a time traveler. You do not have the ability to break the rules of the network, steal cryptocurrency from others, or create new currency out of thin air.

To understand more, let’s go over how we might perform a 51% attack (hypothetically, of course).

A 51% Attack Requires a New Blockchain “Fork”

To initiate a 51% attack, we need to “fork” the blockchain, which means splitting it in two. Then we need to convince the network that our malicious forked blockchain is the real one.

Background reading: What is a hard fork in cryptocurrency?

But there’s a problem:

Cryptocurrencies need to have a way of knowing which blockchain is the ‘real’ one. 

Working this out is very simple – the longest one wins. By going with the longest blockchain on the network, the network can always be sure that the current blockchain is what the majority of the mining power wants. 

The longest blockchain being the ‘real’ one has some other benefits too. 

For example, cryptocurrencies are often community driven. If the community does not like a particular update, miners won’t switch to the new software. If miners don’t switch to the new software, the old chain continues and remains the ‘real’ blockchain for the network.

Making Our Malicious Forked Chain the Dominant One

Essentially, to perform a 51% attack, we need to keep our fork secret. 

We can keep our fork either secret to one computer, or let it go between the nodes we control. Once we have our fork, we need to keep it up to date with the rest of the network.

Essentially we create a mirror image of the original blockchain.

51% attack fork
Credit: CoinMonks

You can think of our secret blockchain as a reset button. Once we have it, we can do something on the live blockchain and not copy it into our secret one. 

Then, we can mine a bit harder on our secret blockchain and have it be a little longer than the real one. That’s why we need 51% of the hashing power on the network.

Nodes in a cryptocurrency network always follow the longest chain, as it usually indicates what the network at large wants to do. Once we release our secret blockchain to the network, all the nodes grab it and see it as the real one, as it’s the longest. 

And once our blockchain is the real one, whatever we did before is undone.

How Double Spending Comes In

Often the thing undone in 51% attacks is a transaction. We can pay for something and then switch out the old blockchain with our secret one where the cryptocurrency is instead transferred to a different address. 

This is referred to as a double spend. The network will reject the original transaction, as it will occur after the new transaction from the perspective of the new blockchain.

What a 51% Attack Can and Can’t Do

As mentioned above, the attack does not give us the power to do whatever we want. 

We must still follow the rules on the network. If we don’t follow the rules, our new blockchain is rejected by the network, and the attack fails. The requirement to following rules makes for an interesting combination of what we can and can’t do during the attack.

What the Attacker Can Do

Cause double spends

This is one of the main reasons to perform a 51% attack. It allows us to spend currency twice, essentially stealing it back from the first address it is sent to. Note that this cannot occur without cooperation from whoever owns the currency in the double spend.

Collect block rewards and cause other miners to have invalid blocks

As the attackers, we are mining all the blocks on our malicious blockchain and therefore get to select where the rewards for mining those blocks go. Depending on the price of the cryptocurrency in question, this may provide a nice counterbalance to the inevitable price-collapse of the cryptocurrency when the attack is revealed. 

Other than some counterbalance, the block rewards are unlikely to completely negate the cost. For this reason, an attack is unlikely to take place solely for the reason of collecting block rewards.

Stop transactions for a time, or remove confirmations from being added to the blockchain

As we control all the blocks in our chain, we can choose what transactions go into those blocks, much in the same way regular miners can. We simply instruct our miners to not include a specific transaction in their blocks. 

The transactions that are kept out of blocks will remain in the transaction pool. After the attack, any miner can pick up the transaction and include it in a block. This means we can delay a transaction for as long as we are in control.

What the Attacker Can Not Do

Steal cryptocurrency from others

As an attacker, we may control the blockchain itself during the time in the attack, but we do not control wallets we don’t own. Having control over the blockchain does not magically give us the private keys required to spend currency we don’t own.

Create cryptocurrency out of nothing

As mentioned above, we must still follow the rules of the network. That means mining blocks and receiving rewards as normal. We can’t magically create non-existent transactions or create cryptocurrency out of nothing.

Completely stop a transaction from occurring

We can keep a given transaction out of the blocks on our chain. But, this does not mean the transaction no longer exists, it simply means it remains in the transaction pool as an unconfirmed transaction. As soon as the attack stops, other miners may pick up the transaction and include it in their next block. Assuming it’s not a double spend transaction at that point.

bitcoin mining energy consumption

It’s a tough time to launch bitcoin mining hardware. As Block Explorer recently reported, bitcoin mining profits turned negative earlier this year. Not only that, but pressure is building over the energy consumption and environmental impact of bitcoin mining.

But that hasn’t stopped Bitmain, the world’s largest bitcoin mining company, from building the next-generation mining equipment.

Bitmain’s new ASIC miners are set to launch Thursday 8th November, but will they reduce energy consumption?

ASIC explained: ASIC miners, or Application Specific Integrated Circuits, are super-powerful processing chips that focus on just one task, in this case, cryptocurrency mining. They are different to normal graphics cards or computer chips which are multi-purpose.

Everything we know about the new Bitmain ASIC Miners

Bitmain is launching two new devices on Thursday: the S15 and T15

Specific details, however, are sparse. We don’t yet know the price, features, or specs of the two devices.

Bitmain has only eluded to the launch via a tweet and empty product pages

Will the new Bitmain Miner Reduce Energy Consumption?

Bitmain’s co-founder and CEO Jihan Wu revealed some information about the forthcoming technology in a speech in September.

He suggested the new miners would “achieve a ratio of energy consumption to mining capacity that is as low as 42J/TH.”

To put that in perspective, Bitmain’s current top-of-the-range miner (Antminer-S9) runs at 96J/TH. In other words, the new miners are significantly more energy efficient than its predecessors.

The current Bitmain Antminer S9

Environmental Impact of Bitcoin Mining

The news comes in the same week as a new research paper which claims bitcoin mining is three-times as expensive as mining the same value of gold.

A further study suggests bitcoin mining consumes the equivalent amount of energy as the entire country of Austria.

The new Bitmain miners may go a small way to lowering the very real impact of bitcoin mining on the world around us. 

7nm Chip Technology

The extra efficiency comes from Bitmain’s new 7nm chip technology. As explained by Jihan Wu, the 7nm Finfet technology is more powerful and more efficient than before. With “more than a billion transistors,” it ushers in a “new era of high-efficiency.”

Of course, nothing is confirmed until Bitmain reveals the full specifications of the new models. Expect more details when the miners are made available for purchase tomorrow.

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who to follow in crypto?

Edit: This list of crypto experts was updated on January 11th to reflect the industry in 2019.

So-called crypto experts are everywhere in the blockchain world. But it’s not always easy to spot the true influencers from the wannabes.

We crawled dozens of “cryptocurrency experts” lists and hundreds of self-proclaimed crypto gurus’ Twitter profiles to distill the data into Block Explorer’s own definitive list of blockchain experts to follow. 

Some are well-known figures shaping the future of the industry. Others are low-key insiders that truly have an immense value to share. So here it goes, the 23 crypto experts you have to follow on Twitter: 

#1 Vitalik Buterin (@vitalikbuterin)

Who? Genius Canadian programmer of Russian origin, creator of Ethereum and co-founder of Bitcoin Magazine. 

Why follow? He’s at the heart of Ethereum’s cutting-edge development, knows the industry’s nitty-gritty and he’s funny, in a dry, sarcastic kind of way. 

What does he say?

#2 Charlie Lee (@SatoshiLite)

Who? The creator of Litecoin. Former director of engineering at Coinbase. Managing director of the Litecoin Foundation.

Why follow? Shares great and easy-to-comprehend bits of information explaining the beauty of blockchain technology to non-tech-savvy blockchain enthusiasts. Also, he is very social and spends time with the most important people in the industry, so you get to know all the experts.

What does he say? 

#3 Jed McCaleb (@JedMcCaleb)

Who? The creator of Mt. Gox (though he left before it was hacked and went bankrupt) and one of the founders of Ripple. Currently developer at Stellar and co-founder of Stellar Development Foundation. Fascinated by octopuses.

Why follow? One of the brightest developers in the field. Tweets are rare but feature the important updates from Stellar on the way to crypto’s mass adoption. 

What does he say?


#4 Roger Ver (@rogerkver)

Who? Among the world’s first investors in Bitcoin startups including,, Zcash, BitPay, Kraken, Bitcoin Cash advocate. 

Why follow? Interested in some popcorn-worthy debates, involving the sharpest minds in the industry? Then enjoy the regular performances in the comment section for some of Ver’s tweets, in a vivid manner explaining why Bitcoin Cash is far way better than Bitcoin. 

What does he say?

#5 Tuur Demeester (@tuurdemeester)

Who? Investor, fintech analyst, the founder of bitcoin fund called Adamant Capital.

Why follow? Shares some great perspectives on trading crypto (and securities) with lots of relevant data and research from authoritative sources.

What does he say?

#6 Andreas M.Antonopoulos (@aantonop)

Who? Entrepreneur, coder, atheist, pacifist, pilot. Author of: Mastering Bitcoin, The Internet of Money, Mastering Ethereum.

Why follow? For all the people out there who are still struggling to understand what bitcoin is and how blockchain works, Andreas is the go-to guy for perfectly clear explanations. His latest book ships at the end of the year. 

What does he say? 

#7 Nick Szabo (@nickszabo4)

Who? Blockchain, cryptocurrency, and smart contracts pioneer (and possible Bitcoin creator?!)

Why follow? Shares some profound thoughts on the blockchain and its potential place and role in the current political, social, and financial systems. On top of that, from time to time, adds some technical insights for those who want to understand the concepts of the blockchain and smart contracts deeper.

What does he say? 

#8 Gavin Andresen (@gavinandresen)

Who? Bitcoin developer, the founder of Bitcoin Foundation. 

Why follow? His tweets are appealing both for crypto traders and developers. Gavin is also witty. 

What does he say? 

#9 Barry Silbert (@barrysilbert)

Who? Founder at Digital Currency Group, “parent” of Grayscale Investments’ Bitcoin and Ethereum trusts and CoinDesk. Also, he’s an investor in more than 100 different cryptocurrencies.

Why follow? Barry’s vast involvement in the field gives him a notable edge on knowing which news to follow and which new cryptocurrencies are worth taking a more in-depth look.

What does he say?

#10 Nicolas Cary (@niccary)

Who? Founder of Blockchain wallet, the chairman and co-founder of Youth Business USA.

Why follow? One of the first people in the industry who actually built a working product (with 29+ million wallets created at the moment of writing this article) and who continues its development. 

What does he say?

#11 Emin Gün Sirer (@el33th4xor) 

Who? Hacker and the professor of computer science at Cornell University.

Why follow? Shares some non-trivial and easy-to-digest ideas that can be appreciated by academics and non-technical audiences alike. If you’re striving to learn more about blockchain and dig into some real questions that the industry still has to solve, he’s worth a follow.

What does he say?  

#12 Adam Back (@adam3us)

Who? Cryptographer, inventor of Hashcash, the proof of work algorithm used in bitcoin mining, co-founder of Blockstream.

Why follow? Perfect if you want to follow the latest developments in blockchain (from the tech perspective).

What does he say? 

#13. Meltem Demirors (@Melt_Dem)

Who: According to her Twitter profile, Demirors teaches at The Massachusetts Institute of Technology and Oxford University. She has a prominent corporate background as an analyst at Dow Chemical and Tradax Energy and as a consultant at Deloitte.

Starting from 2015 she was deeply involved in Digital Currency Group, one of the most active investors in the industry (its portfolio counts over 100 companies). Currently, she is chief strategy officer at investment management company, CoinShares. So she really knows her stuff.

Why follow: Meltem has a UNIQUE point of view on what’s going on in the industry right now and where it might take us soon on the macroeconomic level. And she doesn’t hesitate to share it.

What does she say?

#14 Brock Pierce (@brockpierce)

Who? Chairman of Bitcoin Foundation, involved in a long list of projects including (Re)start, ONE, Blockchain Capital, EOS, DNA, Tether, Mastercoin. 

Why follow? As his own Twitter profile states, Brock is “working to positively impact the lives of billions of people.” A controversial figure, but definitely worth a follow.

What does he say? 

#15 Ari Paul (@AriDavidPaul)

Who? Co-founder of BlockTower Capital. 

Why follow? An expert with in-depth knowledge of blockchain and cryptocurrencies, putting the tech in the perspective of markers, mass-adoption, and regulations. At the moment of writing, Ari decided to take a break from Twitter, but we really hope he’ll be back soon with more insights.  

What does he say?

#16 Jimmy Song (@jimmysong)

Who? Bitcoin educator, developer, and entrepreneur.

Why follow? One of a few people who truly understands the insides of a blockchain and at the same time clearly (and sometimes with a hint of a perfect sense of humor) articulate it to a broader audience.

What does he say?  

#17 Peter Todd (@peterktodd)

Who? Applied cryptography (also called blockchain by some cool kids) consultant.

Why follow? He is sarcastic and geeky, his tweets are right to the point, and he is passionate about tackling some of crypto’s underlying problems like scaling and privacy. 

What does he say?


#18 Eric Voorhees (@ErikVoorhees)

Who? Chief Executive Officer (CEO) of ShapeShift.

Why follow? One of the oldest players in the industry. Shares the most important news and developments in the field of the blockchain that step-by-step lead to crypto assets becoming mainstream. 

What does he say?

#19 Laura Shin (@laurashin)

Who? Forbes editor and host of two crypto podcasts, Unchained and Unconfirmed.

Why follow? She has interviewed and grilled most of the names on this list, asking them tough questions and removing the hype from blockchain. Just listen to her podcast with Binance founder CZ.

What does she say?


#20 Tone Vays (@ToneVays) 

 Who? Derivatives trader, analyst, and blockchain content creator, including the podcast called CryptoScam.

Why follow? For many years Tone worked on Wall Street and even became vice president at JP Morgan Chase after the 2008 financial crisis. The expertise he acquired in the institutional world and his passion for cryptocurrencies are definitely making him a viable candidate for any “best crypto experts to follow” list.  

What does he say? 

#21 Naval Ravikant (@naval)

Who? Co-founder of AngelList. And, as one of the founders on a project Naval advised put it, “he’s the f*cking man.”

Why follow? A person who knows all the nuts and bolts of entrepreneurship. Naval’s tweets are a combination of philosophy, practicality, and inspiration. He also intervolves Bitcoin in this ravel of awesomeness.  

What does he say?

#22 Nathaniel Popper (@nathanielpopper)

Who? The New York Times journalist, reporting about technology and finance, the author of Digital Gold, the most exciting history of Bitcoin.

Why follow? Nathaniel writes the most interesting, in-depth, and entertaining stories about the industry. No kidding. 

What does he say?

#23 Jameson Lopp (@lopp)

Who? Professional cypherpunk, creator of, infrastructure engineer at Casa.

Why follow? Along with techy mambo-jumbo that many of the people involved in crypto will appreciate, Jameson spreads profound knowledge, aimed at a broader audience. Anything from funny comics, curious thoughts and eye-opening metaphors will do in the second case.

What does he say?

#24 Changpeng Zhao (@cz_binance)

Who? Founder of Binance, the largest bitcoin exchange in the world by volume.

Why follow? Insight into what’s going on at the world’s biggest crypto exchange (and the occasional funny tweets towards Elon Musk!)

What does he say?

Do you think we left someone behind? Go ahead and share your favorite crypto expert in the comment section below.

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bitcoin ETF Wall Street

Could a bitcoin ETF finally see approval this week?

Well, I wouldn’t get too excited, but we have reached another important moment in the bitcoin ETF decision process.

November 5th marks the deadline for public comments on nine proposed ETFs. After today’s deadline, the Securities and Exchange Commission (SEC) will make a decision to approve or deny.

So, what do you need to know?

1. The Nine Bitcoin ETFs Were Previously Rejected

The SEC will consider nine bitcoin ETFs this week; two from Proshares, Five from Direxion, and two from Granite Shares.

All nine were rejected back in late-August.

The reasons for rejection were not rooted in concerns over bitcoin itself. Rather, the SEC is worried about manipulation, fraud, and a comparatively small market size.

Further reading: What is a Bitcoin ETF? (And Will it Trigger a Bitcoin Price Surge?)

2. The SEC Decides to Review the Decision

In a strange twist, SEC Commissioner Hester Pierce tweeted shortly after the initial rejection. She implied the decision was made by SEC staffers, and the Commission would now review the applications on a higher level.

Hester Pierce SEC bitcoin ETF tweet

3. New Rules Introduce Public Comment

At the same time, the SEC introduced a new process whereby “interested parties” were invited to comment on the proposed bitcoin ETFs.

“Accordingly, IT IS ORDERED, pursuant to Commission Rule of Practice 431, that by November 5, 2018, any party or other person may file a statement in support of, or in opposition to, the action made pursuant to delegated authority.”

The deadline for these public comments is November 5th.

The SEC may, therefore, reveal its decision at any point in the coming days, weeks, or months.

4. “Godfather of ETFs” Says Approval is Coming “No Time Soon”

Reggie Brown, the so-called “Godfather of ETFs” and senior managing director of Cantor Fitzgerald (a prominent ETF firm) is bearish on the prospects of an ETF approval.

While speaking at a Georgetown University conference last week, he said, “it’s very difficult for the Commission to wrap their heads around a positive approval because there’s no data yet…the markets just aren’t here.”

5. Approval in 2019?

It’s widely considered that forthcoming ETF proposals from VanEck and Solid X have a better likelihood of approval. Not only are they based on physical bitcoin (rather than bitcoin futures contracts), the two companies have significant experience with launching and running ETFs.

While their initial proposal was rejected earlier this year, the group will submit a follow up in 2019.


We expect to hear a decision from the SEC in the coming days or weeks, but don’t hold your breath. The bitcoin and cryptocurrency market has not sufficiently evolved since the previous rejections, so we’re unlikely to see a change of heart just yet.

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