When was Bitcoin released to the public for mining and use

Bitcoin was released to the public for mining and use on 3 January 2009, in accordance with its planned schedule.

Many of the main characteristics that make up Bitcoin are determined by the cryptographic protocol implemented within it. Among them are: timestamping, security, and availability. The creation of a new bitcoin is tightly coupled with these factors, so there can be no artificial inflation; once any particular bitcoin is spent or transferred, it becomes impossible to re-spend without invalidating its history, i.e., without breaking its DNA code.

The most obvious consequence of this inability to counterfeit bitcoins is the scarcity of coins in circulation; Bitcoin issuance will eventually stop when 21 million bitcoins have been generated – approximately around 2140.

Another characteristic is the blockchain, a transaction log of every bitcoin that has been issued and passed. This log may be viewed and verified on a public distributed ledger database in real-time at any one of thousands of sites around the world. The blockchain database is constantly growing (currently at 5+ per minute) and represents a complete history of every bitcoin that has ever existed. That history can be examined to monitor bitcoin flows, spot patterns, or find out how certain bitcoins have been transferred.

The Bitcoin software itself is available for inspection, but cannot be re-purposed to create new bitcoins because it contains no mechanism for issuance, unlike traditional currencies such as dollars or euros. New bitcoins can only be generated by computer code. Bitcoins can be mined by solving cryptographic puzzles, but the code that does so was designed in such a way that stopping it is extremely difficult.

The software that powers Bitcoin is a fanatically fault-tolerant piece of open-source software called "Bitcoin Core". The code was largely written by Satoshi Nakamoto (possibly an alias for one or more people), a pseudonymous programmer who left no trace of his/her real identity. Some have speculated it to be a pseudonym for either the Japanese mathematician Shinichi Mochizuki or another pseudonymous programmer, Hal Finney. It uses peer-to-peer networking and cryptographic proof to facilitate instant payments, but the public ledger of every bitcoin transaction is publicly accessible and checked by thousands of computers around the world.

The third characteristic is security. Bitcoin is designed with several cryptographic algorithms (such as SHA256) that make it difficult to counterfeit. Even under cryptanalysis, which is already difficult because transactions are always cryptic, it's hard to find a way to successfully change or reverse legitimate transactions. Bitcoins can be stored in a variety of ways, including digital wallets like Blockchain Bitcoin Wallet and the various versions of the Bitcoin Core software (though there are also bitcoin paper wallets), or physical offline storage such as in a USB drive or paper wallet.

Paper wallets are a relatively simple way of storing bitcoins offline and securing them against theft and loss. They have the advantage that the private key is not loose, but is printed out on paper – hence "paper wallet" – and so cannot be transferred electronically. A paper wallet was considered lost when a computer system was infected by malware in 2012 and the backup seed key kept on the same system disappeared because of a software bug. The first known case of bitcoins lost due to a failed paper wallet occurred in 2011 when one user claimed to have lost 7500 bitcoins worth $500,000 at today's value.

All of these characteristics make it extremely resistant to fraud, counterfeiting, and theft – not only because of the digital nature of the transactions that are made but also because of the open source code which makes it easy for independent and objective parties to independently verify that no one is stealing bitcoin or trying to defraud it.

When Bitcoin was released on 3 January 2009, there was approximately 50,000 bitcoin that could be mined. Today, there are approximately 12 million bitcoins in circulation and around 12 million bitcoins remain unmined (of which 5.5 million have been generated since bitcoin first came out). This represents an annual loss rate of 6% and a contraction rate over time of 3%.

The rate at which Bitcoins can be created is automatically halved every four years. Originally, the reduction was 50% every four years until it hit 1 in the year 2016; it then dropped to 25% every four years, and will later drop to 12.5%. This gradual rate of contraction means that Bitcoin will one day become extremely deflationary – there will only ever be a maximum of 21 million bitcoins.

In his famous October 31, 2014 letter to the community, Satoshi Nakamoto hinted at how this virtual supply of currency would be managed: "Once a predetermined number of coins have entered circulation, new coin generation ceases. Thereafter, only coin transfer transactions are permitted. The content of the currency relies on voluntary donations by its users. A well-functioning economy will be self-regulating and free from central control."

Since its inception, there have been many attempts to hack or otherwise misuse Bitcoin – especially in 2013 and 2014, when the price of bitcoin was growing rapidly. For one to compromise a bitcoin system, one would need to first transfer control over at least some part of it; such an attack can be made only by gaining control over some computer that is connected to the Bitcoin network. The remainder is relatively secure because they are all in closed networks: mining pools and other systems manage them, generate them and divide them up among those systems. Bitcoin advocates believe it's unlikely that anyone will be able to breach all of those systems to attack the network as a whole.

The Bitcoin network is hardly perfect and far from infallible. It is not impervious to hackers: malware attacks, bad actors, and other issues are a constant concern for users. However, the nature of the system means that even if a security vulnerability does exist, any attempt to exploit it would be met with swift negative repercussions for the thief (even if he/she succeeded at stealing some bitcoins). This security model makes it difficult for anyone but individual users to compromise a bitcoin wallet or blockchain – though not impossible.

In four years of existence, bitcoin has undergone a process of trial and error that has seen the open-source community try and largely succeed at solving many of the bugs that would have allowed one to compromise the system. The possibility of just such an attack could explain some of the volatility observed in bitcoin pricing.

The decentralized nature also makes it difficult for governments to control or regulate it. Anonymity is one of its key features, which makes laundering money through bitcoins very easy – though, not impossible. A high-profile case is a WannaCry ransomware. At least three samples of it included links to a bitcoin address and wallet, which bitcoin experts believe were "decoys" intended to distract users. The link was supposed to trick victims into making payments that would go to the attackers. According to a blog post by Bitdefender,

"The ransomware creators are likely after Bitcoin ransom payments in an attempt to make this attack (cybercriminals and malware authors are always looking for ways to monetize their efforts), but there's little evidence that they've gotten much at all if anything. Despite some reports, there's nothing to indicate that the WannaCry attackers have made off with any funds."

The Bitcoin network is truly revolutionary in its approach to transparency and accountability. Every transaction ever made, since the first one in January 2009, is available for all to see on Blockchain.info or any other bitcoin explorer. If a party wanted to prove that it did not own a bitcoin address or that it had never received bitcoins from someone else, it could easily do so.

Bitcoin is also self-policing. In a sense, it is like a bee colony: if one bee attacks another, that bee must leave and never come back to the hive. If a bad actor attempts to defraud the system in any way, he will be immediately exposed and ostracized by the community. This accountability makes it extremely difficult for anyone to commit fraud with bitcoin.

In summary, these are some of the principal characteristics that make Bitcoin so secure:

A high volume of transactions

The fact that transactions cannot be changed (they only can be added to) means that once a transaction has occurred, it is verified forever; no one can change it later on. Public ledger

All of the transactions are public and visible to all users – they cannot be hidden behind secretive dealings. Proof-of-work system

This system engages all participants in its maintenance, making it extremely difficult to compromise (for example, an attacker would need more computing power than the rest of the network combined). Unique addresses

Each bitcoin address is unique and can only be used once. Each can only receive and send a certain amount of bitcoins at one time. This prevents the reuse of payment addresses. The approach to creating addresses is also unique in that it allows a Bitcoin user to create a new address simply by generating a new random number and subdividing that number by one million places. This makes it more secure than other methods as no one can monitor or predict the future use of transaction information. Mixing services

These services essentially "mix" transactions together, making it extremely difficult for anyone to track the flow of any particular bitcoin from its source to its ultimate destination (although, not impossible!). P2P network

Because the network is peer-to-peer, no single entity or entity can determine when a transaction is taking place (except for malware in the case of unencrypted wallets). Anyone can join the network and contribute computing resources to make sure that it operates smoothly. Open source code

All of the code for Bitcoin's protocol and security is available freely online. Even though you may have heard otherwise, this is not "Bitcoin Core", but rather "Bitcoin Core/ASICs". No owner

There is no central party that has control over it. The network follows a set of rules that are not controlled and cannot be changed by any single party. Decentralized

The power to manage bitcoin is decentralized. There is no single "bank" that can freeze, block or manipulate its transactions. All of the major decisions and changes made are democratically agreed upon by the majority of participants. Open source code

All software used for the Bitcoin protocol and security is available freely online at GitHub; clients are also open source (although they may contain proprietary binaries).

The powerful combination of these characteristics makes it impossible for any entity to gain control of the system and therefore it's "impossible" to defraud. Furthermore, it cannot be controlled by any single entity. This is why Bitcoin is so revolutionary. The total of its characteristics makes this digital asset an extremely secure way to transfer value from one party to another.

I hope that you now understand the inherent security behind Bitcoin, not that you ever thought otherwise! If there's anything I have left out or misunderstood, please leave a comment and I'll add a footnote. Thanks for reading!