Symmetric Key Cryptography

Cryptography in our times is experiencing a real heyday - now it is no longer only the prerogative of the military and security specialists, but also a full-fledged science with its own theoretical apparatus, principles and rules. And all because in modern society, information is almost more valuable than real money.

At the current moment, there are two fundamentally different areas of cryptography - with an asymmetric key and with a symmetric key. Both of these areas are being actively developed and sometimes combined to better address pressing digital security challenges. But the first one was exactly symmetric key cryptography, so that's what we'll talk about now.

What is it?

In short, this is any algorithm that uses the same code for encryption and decryption. It can be transferred to the other party, but exclusively via secure data transmission channels. And only to those people who can be trusted.

Usually, both the sender and the receiver know the principle of the encryption algorithm and the only thing they need for normal operation with the transmitted information is a common key. Since it is randomly selected, it is quite difficult to hack it, so its length is not that long - from 128 to 256 bits.

What are the main options?

There are several basic algorithms for such encryption:

• Simple transformation
• Single key transformation
• Double transformation
• "Magic Square" Method

Also, all such cyphers are divided into 2 large groups:

• Blocky. The data is processed in blocks of a predetermined length, each block undergoes several mixing cycles - rounds.
• Streaming. Each bit or byte of information is processed sequentially. The method is more complex and is based on block encryption.

Advantages and disadvantages

Symmetric encryption is the very first information encryption method invented by mankind. That is why it is characterized by the following advantages:

• High speed of work
• Ease of implementation of algorithms
• High level of stability guaranteed by a shorter key
• Predictability and knowledge

However, it also has disadvantages. The main one is the complexity of the key exchange. This information should be transmitted exclusively over secure channels so that no one else can use it. It is also imperative that each machine used, usually meets high safety standards.

Modern use cases

Symmetric encryption is at the heart of most information security principles in modern computer systems. For example, the Advanced Encryption Standard (AES) is used by the US government to protect highly sensitive confidential information. A similar method is used in CIS countries - GOST 28147-89. And the 3DES algorithm, for example, has been used to provide security in the electronic payments industry for a long time. In addition, these encryption methods often underlie more modern hybrid cyphers that combine both symmetric and asymmetric approaches.