Human society throughout its existence has realized that the data which it operates with could be important or not. Their importance depends on the information contained in the data set. Important information often requires that the circle of people using it remains narrow or expands as the owner or proprietor wills it. But now the question arises, how a person can protect his data, or limit the circle of people who can use this data. In order to answer this question, a whole science called cryptography has appeared.
Cryptography is the science of methods for ensuring confidentiality (the impossibility of reading information by outsiders), data integrity (the impossibility of discreetly changing information), authentication (verifying the authenticity of authorship or other properties of an object), as well as the impossibility of non-repudiation. The history of cryptography is about 4 thousand years old. I don’t want to delve into its history, but only talk about the first encryption algorithms and then move on to examples from the modern world. The first encryption methods were mono-alphabetic, that is, their main principle was to replace the source text with another alphabet by replacing letters with other letters or symbols. This method is quite interesting, but if the encrypted text is large, then you can easily choose the alphabet with which this text was encrypted. From this example, we can conclude that coming up with a strong encryption algorithm is a rather difficult task and even today there is a lot of work to explore in this area.
If you think about why people need to protect information in this way, then an example of military operations immediately comes to mind. During them, there is a need to transfer important information through unreliable communication channels and if we can do nothing aboutt improving the data transmission channel, then we can protect the information itself by encryption. This example shows that good encryption can decide the outcome of hostilities. But if we exclude any military conflicts, the question arises: do we use encryption in peacetime, that is, in our everyday life? And I will answer that with the development of modern means of communication and technology, this has all become automatic and an ordinary person may not even realize that the data that he sends over the Internet or over the phone is encrypted.
Attackers usually need to get to your passwords, for example, on social networks or other web applications, which may contain important information for you. As well as passwords for your bank cards, their electronic signatures may be of the interest to attackers. And just imagine the criminal who got to the information that you send to the server after any transaction on the Internet. What joy he will experience if he sees your password in the form of a "password". But this certainly will not happen, because modern online stores use very strong encryption, which is very difficult to crack. And now we know that the information that we transfer to the server is not like the original text, but it looks like something incomprehensible and illegible.
“5f4dcc3b5aa765d61d8327deb882cf99” our password will look like this if we encrypt it using the md5 algorithm. Of course, more complex algorithms are used in this situation, but as an example, it fits very well. And every year these encryption algorithms become more complex, or new ones are invented.
The most popular encryption algorithm is the RSA algorithm. RSA algorithm is asymmetric cryptography algorithm. Asymmetric actually means that it works on two different keys i.e. Public key and Private key. As the name describes that the Public Key is given to everyone and Private key is kept private.
An example of asymmetric cryptography :
A client (for example browser) sends its public key to the server and requests for some data.
The server encrypts the data using client’s public key and sends the encrypted data.
Client receives this data and decrypts it.
Since it is asymmetric, nobody else except browser can decrypt the data even if a third party has public key of a browser.
Since we have only examined a small fraction of the use of cryptography, you can understand that its applicability in the modern world is huge. If not for cryptography, then any person who would like to steal our data, could do that.