Brief intro to cryptography

Hi everyone,

this edition will be another, today it will be an introductory post to cryptography

In our daily lives, cryptography is everywhere: it secures your connection to your favorite websites and keeps your passwords or banking account secret. As our lives are more integrated into the digital world, security with the privacy of data is coming one of the essential things, and cryptography plays a unique role here.

Modern cryptography is based on publicly known and standardized algorithms. Their public availability is effective in that vulnerabilities in them can be found and announced faster. Hence the security of modern cryptography is not depending on the secrecy of the algorithm but on the secrecy of the key, according to Kerckhoff's principle:

"The system should be designed to be secure, even if all its details, except for the key, are publicly known"

One of the most common algorithms today is AES. It is a symmetric key cryptography algorithm. To encrypt or decrypt data all parties need to have the same key. Obviously, the key should be kept and distributed secretly. Nowadays to distribute symmetric keys securely usually use Diffie–Hellman key exchange or some other asymmetric-keys algorithm

The main difference between symmetric and asymmetric algorithms is that the second has two keys: one is a public key and the other is a private key. With the public key, you encrypt messages and decrypt them with the private key.

In modern state cryptography, cryptographic algorithms are not used on their own, but as complex systems/protocols. It solves the drawbacks of each type of algorithm:

e.g. symmetric-key algorithms encryption is much faster than asymmetric and the key length is smaller as well. E.g common key length for symmetric encryption algorithm AES is 128 or 256 bits but for RSA is 2048 or higher

and moreover, the size of encrypting text after using symmetric cryptography is usually the same as plain text unlike asymmetric, which is much larger

but the asymmetric algorithm is useful for key distribution.

a good example of their application is TLS handshake where the client and server exchange secrets with an asymmetric key algorithm and then generate session keys for symmetric encryption

With the development of computing power, such a phenomenon as quantum сomputing appeared. Quantum computers store data in quantum bits - the quantum version of the classic binary bit physically realized with a two-state device. This allows the computation to be much faster than traditional processors.

And all this introduces a new concept of post-quantum cryptography.

Most symmetric ciphers are quantum-safe, which means they are not breakable with a quantum computer. It only needed to increase the key length.

What you can't say about asymmetric cryptography, which is mostly based on non-solvable yet mathematical problems but which could be solved with quantum computers in the future.

That is all for today, just a brief introduction to cryptography, next, I plan to touch on a few technical details/concepts of this topic.

I hope you like this post

Alex