Indeed, we said it. Blockchain Technology!
More than just another word to understand, Blockchain is the root of any cryptocurrency.
The Blockchain is a chain of blocks stored in a public database. The blocks will store information about transactions (date, time, amount of the transaction, participants of the transaction). Once a block is created, it cannot be erased or rolled back.
A single block on the Bitcoin blockchain can store up to 1Mb of data, so approximately a few thousand transactions.
A transaction is known immediately by the whole network. However, a transaction needs to be confirmed before the coins appear in the receiver’s balance. This process is used to add a layer of security and avoid double-spending problems.
To summarize, if you want to send Bitcoins to a friend, you will have to ask him his Bitcoin (BTC) Address. Then, you will send your Bitcoins on his address. The transaction will then appear on the Blockchain and is accessible by everyone. However, your friend will have to wait for the validation of the block to spend the Bitcoins.
So, anyone can view the contents of the Blockchain, but knowing your address will not allow anyone to know it belongs to you. A Blockchain is not private, nor anonymous, but a system using addresses as “nicknames”.
The Bitcoin blockchain is known to be Proof-Of-Work. Computers must “prove” they worked by solving a complex math problem; when solved, it becomes eligible to add a block to the Blockchain. This process is called mining. This system makes attacks by hackers useless. A hacker would need to control more than 50% of all the computing power on the Blockchain to breach it. This type of hack is called the 51% attack. Considering the power distribution of the Bitcoin Blockchain technology, the risk is shallow for this attack to occur. However, this event can happen on less secure blockchains.