Attacks in the World of Cryptocurrencies

You must have heard of "51 percent attack", "double spend" and other frightening phrases that disturb cryptocurrency-related communities. Although such caution is not unfounded, the fuss together with ignorance give rise to numerous rumours. Are Bitcoin and other digital currencies in danger? Let's clear things up and review the most widespread attacks that might affect the sphere.

51% Attack

We cannot help starting with the most familiar attack, which was described in the article by Satoshi. This one covers a situation when someone (one person or a group) has more than half of all the mining powers in the network.

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Sidechains: How Many Sides Does a Cryptocurrency Have?

Bitcoin is wonderful. Bytecoin is wonderful. Dogecoin is wonderful. All cryptocurrencies are wonderful (well, let us think for a moment that it is true).

You can pay Bitcoins for sandwiches in Subway, use Bytecoins for private purchases, send Dogecoins to your friends as gifts and so on. That is, you can use features of each cryptocurrency for suitable cases. But - what a nuisance! - you would not like to keep a dozen wallets with all these coins.

Naturally, you can just make another cryptocurrency, which will combine all the best features. A kind of a standard for cryptocurrencies. Wait... it reminds me of something...

sidechains and cryptocurrencies

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What is Privacy and Why is It Important?

This is a guest post by Edvin Dahlstrom

Is privacy good or evil? Does any person have a right to be privacy-protected? Can we apply common statement "If you are doing nothing wrong, you have nothing to hide" to our lives?

Right now, society is desperately looking for the answers to these particular questions, but it seems that government has solid position regarding them, too. Lack of privacy in our lives seems to be relatively farfetched problem for the majority of people, but eventually debates could turn into a serious confrontation. A careful eye would notice that for now there is little resistance.

what is privacy

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The Shifting Nature Of Bitcoin Acceptance

This is a guest post by Amanda Cole

It may be Bitcoin's single greatest achievement that the cryptocurrency has gained name recognition that far surpasses its actual value or utility.

In a way, it's not unlike how many consumers already associate forward-thinking tech giant Tesla with driverless cars, or equate NASA with missions to Mars. Those companies will surely be major players in those respective pursuits, but aren't really there yet. Similarly, Bitcoin has positioned itself to be a significant if not dominant financial resource once the world fully comes around to the idea of digital currencies. But at this point, we're (again) just not there yet.

bitcoin acceptance

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A Greater Giving Potential: Introducing Micro-Donations in Bytecoin

In 2013, following a period of reflection and visioning, I imagined the possibility of completely altering the financial system as we know it. This vision, known as ABIS, will now see its first-ever implementation.

The implementation is now being issued in BCN's GUI Wallet with the release of v. 1.0.8, where the transaction has been re-envisioned to allow the user new ways to explore the possibilities of transactions and realize greater giving potential, initially through two use cases involving unique forms of donations...

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Alternatives for Proof of Work, Part 2: Proof of Activity, Proof of Burn, Proof of Capacity, and Byzantine Generals

This is a guest post by Ray Patterson.

This blog post continues the series of articles on how various cryptocurrencies work. In the previous part we've given the overview on how Proof of Stake is different from Proof of Work and what issues its design causes. To learn more about how various Proof of Work algorithms work, check out "History of Proof of Work" post.

Proof of Work vs Proof of Stake: what else?

Proof of Stake vs Proof of Work

To sum up the arguments of the previous post, the energy efficiency of Proof of Stake is a double-edged sword. On the one hand, the energy is not spent, on the other, the decentralized consensus model seems unstable without these expenses...

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Alternatives for Proof of Work, Part 1: Proof Of Stake

This is a guest post by Ray Patterson.

This is another article from the series of publications on how various cryptocurrencies work. By popular requests this post is devoted to Proof of Work, Proof of Stake, and some other proof-of-something comparison. Make sure to check our previous article, "The Proof-of-Work in Cryptocurrencies: Brief History".

Proof of Work vs Proof of Stake

Proof of Work criticism

As we remember, the Proof of Work was born in the long past 1993, in the cryptographers' family; parents intended it to become the defender from DoS attacks and spam. However, it received an offer it could not refuse by some anonymous with Japanese accent: to become a basis for distributed timestamp server. The scheme seemed simple: network nodes "vote" for their version of transaction history by introducing their computational powers into calculating "rare" hashes. The version that gets the majority of votes is accepted by all nodes as the reference version...

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The Proof-of-Work in Cryptocurrencies: Brief History. Part 2

This is a guest post by Ray Patterson

Read the first part here.

Crossmating: The Altcoin Boom

By the mid-summer of the year 2013, more than a hundred altcoins were up and running, with almost half of them appeared in the latest couple of months. Should we mention that all those 'newbies' were LItecoin forks and utilized scrypt? Another trend of the season was an upstart Proof-of-Stake from PPcoin, so scrypt+PoS combo could be called 'standard alt-coin-beginner package'.

Such (quantitative) popularity of scrypt and exponential growth of Bitcoin complexity led to a simple thought: scrypt-ASICs will appear as soon as they are profitable. Despite the fact that giant November bubble (when Bitcoin was rated up to $1200) was far from beginning to balloon, the search for the new PoW function started again...

proof of work

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The Proof-of-Work in Cryptocurrencies: Brief History. Part 1

This is a guest post by Ray Patterson

Before Bitcoin: Hashcash & Moderately Hard, Memory-bound Functions

The Proof-of-work concept appeared for the first time in the paper "Pricing via Processing or Combatting Junk Mail" in 1993. Despite the fact that authors never used this notion in the article itself (it is 6 years before it appears), we are going to name it this way (or PoW).

So, what was the Idea proposed by Cynthia Dwork and Moni Naor in their paper?..


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On Mixers, Tumblers and Bitcoin Pseudonymity

This is a guest post by Ofir Beigel @

Almost a year ago the Israeli police apprehended a 20 year old computer technician in suspicion of fraud. Of course this story wouldn't have made it to the headlines if it didn't involve the controversial currency Bitcoin.

Here's how the story evolved:

A naive Bitcoin merchant was looking to sell his coins through one of the many Bitcoin trading groups on Facebook. The suspect contacted the merchant and offered to buy his coins from him for a total of $5,000. The merchant agreed and requested that the suspect wire the money to him.

Shortly after, the merchant received a screenshot with the wire confirmation and transferred the coins to the suspect's public address. Having felt that this was "just too easy" the merchant inspected the screenshot in greater detail only to find out that it was fake and didn't actually belong to the suspect's bank account...

Bitcoin Pseudonymity

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