Blockchain Introduction


To understand what Blockchain is, let’s travel to the beginnings of the creation of this worldwide
network of computers, our Internet. Have you ever wondered how the internet works? No?

The global network of computers was designed to share information with other members of this
same network, whether a local network or an external network, in turn this network has a server
(called that name because it is the centralizer of data / information) .
Our internet works that way, several clients (Machines of the users) connected to a network, ask
the server for the data they want and in turn the server returns the requested data, to better
illustrate these procedures let's use Facebook as an example:
When accessing the profile of some user you will see all the data and post it, but underneath the
cloths what actually occurs is the client (user's machine, user's cellular, electronic devices)
requesting the Facebook server all data of a certain profile, the server will process the request,
search, then will verify if the data of that profile is actually available, if they are, the server will
return the data to the client machine and it will show to the user.

A centralized network is characterized by multiple clients (data requesting computers) and a single
server (data provider), this network is called a centralized network by centralizing all the required
information of its clients in a single location. Example: (Facebook, Google+, Hotmail, Uol).

It consists of decentralizing information, not uniting the data in a single place, but distributing this
information to all customers, where they all have some or all of the data that the network needs.

It is a network architecture of computers, where each point or node (nodes) of the network
functions as both client and server (Client / Server), allowing the sharing of services and the digital
data. An example of P2P (peer to peer) networks are the torrents that perform the sharing of this

A Hash function is an algorithm that maps variable-length data to fixed-length data, the theoretical
concept says that "Hash is the transformation of a large amount of data into a small amount of
information", in other words, it will grab the data and submits the function, which will make the
conversion returning another completely different value.

It is the study of the principles and techniques by which information can be transformed from its
original form to another illegible, so that it can be known only by its recipient (the "secret key"),
which makes it difficult to read by unauthorized person.
The Blockchain should be encrypted and tamper-evident, the encryption used is the Asymmetric,
but let's talk of two main ones are:

  • Symmetric key:

Symmetric Key aims to use a single key to encrypt and decrypt the data.
In the symmetric key the same key encrypts and decrypts the message, the problem is that if this
key is owned by an attacker, it can decrypt all of the user's messages.
Disadvantages: Data vulnerability.
Advantages: Shipping process is much faster compared to the Asymmetric key.

  • Asymmetric key:

Two keys are created: one for Encryption of information and one for decrypting, the public key can
be obtained by all.
The Asymmetric key is intended to make the information more secure, that is, the user has a public
key and a private key, publica will be responsible for encrypting and everyone can request the

recipient the message so that if it is intercepted by a hacker malicious, the message can only be
decrypted by its real recipient, because to decrypt it will require a private key.
Disadvantages: Slow
Advantages: Much safer