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Cryptocurrencies and blockchain technology are often regarded as the same thing. This makes it seem like a cryptocurrency cannot exist without an underlying blockchain technology. But is this really the case?
Do all cryptocurrencies use the blockchain?

According to the definition of cryptocurrency, the answer is no. The defining characteristic of any cryptocurrency is that security is ensured with cryptography. Moreover, cryptocurrencies aren’t issued by a central authority, like a bank. In theory, this makes them immune to government interference or manipulation.

Cryptocurrencies pioneered in blockchain technology. And while blockchain has many advantages over traditional, centralized banking systems, some believe that there are drawbacks to certain aspects of blockchain technology, including scalability problems, slow block creation times, mining fees and double-spending attacks.

Non-blockchain cryptocurrency essentials

  • Not all cryptocurrencies are blockchain-based.
  • These include IOTA, Nano, Byteball and others.
  • They are based on directed acyclic graphs, or DAGs.
  • DAGs promise to eliminate mining fees and speed up transactions.
  • DAGs promise to solve the problem of scaling.
  • DAGs are vulnerable to certain types of attacks.

The dawn of DAGs

Bitcoin was the first cryptocurrency to see the light of day, back in 2009. But it wasn’t the cryptocurrency alone that prompted such international interest. Many believe that the more important novelty was Bitcoin’s underlying blockchain technology. Introducing decentralized peer-to-peer blockchains, the technology took the world by storm. For a few years, blockchain ledgers were the defining characteristic of any cryptocurrency. But that all changed with the official launch of IOTA.

IOTA replaced the traditional blockchain-based distributed ledger with a so-called directed acyclic graph (DAG). The IOTA protocol operates with a DAG-based consensus algorithm which the IOTA team have termed Tangle. Though still in development, Tangle is eventually intended to work as a distributed ledger similar to blockchains, but with a unique twist. A trader who makes a transaction must confirm two random previous transactions. Each of these two will have validated two other transactions before, and so on. The end result is not that transactions are grouped into blocks and stored in a blockchain. Rather, it is a stream of individual transactions entangled together.

After the launch of IOTA, many non-blockchain protocols followed suit. However, most of them invented their own consensus algorithms to protect the network from double-spending attacks. Aside from IOTA, protocols utilizing DAGs also include Nano and Byteball.

Each of them puts into practice a different consensus algorithm. Nano, formerly called Raiblocks, implements the so-called Block-lattice. With Block-lattice, every user gets their own chain to which only they can write. Additionally, everyone holds a copy of all of the chains. Every transaction is broken down into a send block on the sender’s chain, and a receive block on the receiver’s chain. The problem of Block-lattice is that it is vulnerable to penny-spending attacks. These involve inflating the number of chains that nodes must track by sending negligible amounts of cryptocurrency to empty wallets.

DAG vs blockchain

Some see DAGs as an alternative that combats the shortcomings of blockchain technology, but it would be false to claim that one technology is better than the other. In the world of cryptocurrency, people often try to build hype around the technology they invested in. This leads to the creation of buzzwords like “blockchain killer,” meant to portray DAGs as technologically superior to blockchain.

While a DAG network does perform better than blockchains in some aspects, it is crucial to consider the advantages and disadvantages of both.

Advantages of DAGs

The main pros of DAG networks have to do with mining. Because no mining takes place, there are no mining fees associated with making DAG transactions. Seeing how block rewards are falling, mining fees are bound to rise in order to incentivize miners to continue mining. In that respect, a system that would eliminate mining fees altogether looks promising for the future.

No mining also means better latency, accounting for faster validation and processing of transactions in the network. Once a node receives a transaction, it can confirm it immediately, without having to wait for a new block to be formed. This may not be as prominent, when compared to blockchains with fast or moderate block times, for instance Ethereum or Litecoin. But when compared to Bitcoin and Bitcoin Cash, the difference in time is more pronounced.

Disadvantages of DAGs

Existing DAG networks are facing security problems because of their current network sizes. To prevent double-spending attacks until their networks grow, each DAG has come up with its own solution. IOTA’s Tangle – though designed to get faster as the network grows – currently relies on a single coordinator node, also called the proof-of-authority node.

Byteball, another DAG-based network, relies on 12 so-called witness nodes that operate a main chain. These witness nodes are controlled by the developer to check the state of the DAG. While IOTA and Byteball claim their solutions are temporary, they’re problematic in terms of centralization, since both of them are, in a sense, operated by a central authority.

Trading DAG-based cryptocurrencies

At the moment, not all DAG-based cryptocurrencies can be bought with fiat currencies like euros and dollars. Most exchanges that support these currencies only allow you to buy them using other cryptocurrencies, like bitcoins or ether. If you don’t already own cryptocurrency, you’ll have to buy some first through one of the relatively few exchanges in the world that allow you to buy cryptocurrencies using your everyday money.

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