What is Cryptocurrency and How Cryptocurrencies emerged as a side product of digital cash

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• What is cryptocurrency
A cryptocurrency is a digital asset designed to work as a medium of exchange that uses strong cryptography to secure financial transactions, control the creation of additional units, and verify the transfer of assets. Cryptocurrencies are a kind of alternative currency and digital currency.

Few people know, but cryptocurrencies emerged as a side product of another invention. Satoshi Nakamoto, the unknown inventor of Bitcoin, the first and still most important cryptocurrency, never intended to invent a currency.

In his announcement of Bitcoin in late 2008, Satoshi said he developed “A Peer-to-Peer Electronic Cash System.“
His goal was to invent something; many people failed to create before digital cash.
Announcing the first release of Bitcoin, a new electronic cash system that uses a peer-to-peer network to prevent double-spending. It’s completely decentralized with no server or central authority. – Satoshi Nakamoto, 09 January 2009, announcing Bitcoin on SourceForge.

The single most important part of Satoshi‘s invention was that he found a way to build a decentralized digital cash system. In the nineties, there have been many attempts to create digital money, but they all failed.
… after more than a decade of failed Trusted Third Party based systems (Digicash, etc) , they see it as a lost cause. I hope they can make the distinction, that this is the first time I know of that we’re trying a non-trust based system. – Satoshi Nakamoto in an E-Mail to Dustin Trammell
After seeing all the centralized attempts fail, Satoshi tried to build a digital cash system without a central entity. Like a Peer-to-Peer network for file sharing.
This decision became the birth of cryptocurrency.

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They are the missing piece Satoshi found to realize digital cash. The reason why is a bit technical and complex, but if you get it, you‘ll know more about cryptocurrencies than most people do. So, let‘s try to make it as easy as possible:
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.

In a decentralized network, you don‘t have this server. So you need every single entity of the network to do this job. Every peer in the network needs to have a list with all transactions to check if future transactions are valid or an attempt to double spend.
But how can these entities keep a consensus about this records?
If the peers of the network disagree about only one single, minor balance, everything is broken. They need an absolute consensus. Usually, you take, again, a central authority to declare the correct state of balances. But how can you achieve
consensus without a central authority?
Nobody did know until Satoshi emerged out of nowhere. In fact, nobody believed it was even possible.
Satoshi proved it was. His major innovation was to achieve consensus without a central authority. Cryptocurrencies are a part of this solution – the part that made the solution thrilling, fascinating and helped it to roll over the world.

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What are cryptocurrencies really?
If you take away all the noise around cryptocurrencies and reduce it to a simple definition, you find it to be just limited entries in a database no one can change without fulfilling specific conditions. This may seem ordinary, but, believe it or not: this is exactly how you can define a currency.
Take the money on your bank account: What is it more than entries in a database that can only be changed under specific conditions? You can even take physical coins and notes: What are they else than limited entries in a public physical database that can only be changed if you match the condition than you physically own the coins and notes? Money is all about a verified entry in some kind of database of accounts, balances, and transactions.
How miners create coins and confirm transactions
Let‘s have a look at the mechanism ruling the databases of cryptocurrencies. A cryptocurrency like Bitcoin consists of a network of peers. Every peer has a record of the complete history of all transactions and thus of the balance of every account.

A transaction is a file that says, “Bob gives X Bitcoin to Alice“ and is signed by Bob‘s private key. It‘s basic public key cryptography, nothing special at all. After signed, a transaction is broadcasted in the network, sent from one peer to every other peer. This is basic p2p-technology. Nothing special at all, again.

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The transaction is known almost immediately by the whole network. But only after a specific amount of time it gets confirmed.
Confirmation is a critical concept in cryptocurrencies. You could say that cryptocurrencies are all about confirmation.
As long as a transaction is unconfirmed, it is pending and can be forged. When a transaction is confirmed, it is set in stone. It is no longer forgeable, it can‘t be reversed, it is part of an immutable record of historical transactions: of the so-called
blockchain .
Only miners can confirm transactions. This is their job in a cryptocurrency-network. They take transactions, stamp them as legit and spread them in the network. After a transaction is confirmed by a miner, every node has to add it to its database. It has become part of the blockchain.
For this job, the miners get rewarded with a token of the cryptocurrency, for example with Bitcoins. Since the miner‘s activity is the single most important part of cryptocurrency-system we should stay for a moment and take a deeper look on it.