Cryptographic systems are currently divided into two main areas of study: symmetric and asymmetric cryptography. Symmetric encryption is often used synonymously with symmetric cryptography, and asymmetric cryptography covers two main use cases, asymmetric encryption and digital signatures.

Therefore we can represent them as follows:

  • Symmetric key cryptography

    • Symmetric encryption

  • Asymmetric cryptography (or public key cryptography)

    • Asymmetric encryption (or public key encryption)

    • Digital signatures (may or may not include encryption)

This article will focus on symmetric and asymmetric encryption algorithms.


Symmetrical vs. asymmetric encryption

Encryption algorithms are often divided into two categories, known as symmetric and asymmetric encryption. The fundamental difference between the two methods is that symmetric encryption algorithms use a single key, while asymmetric encryption algorithms use two different but related keys. This difference, while seemingly simple, represents large functional differences between the two forms of encryption and how they are used.


Key Correlation

In cryptography, encryption algorithms generate keys in the form of sequential bits that are used to encrypt and decrypt a piece of information. The way these keys are used takes into account the difference between the symmetric and asymmetric methods.

While symmetric encryption algorithms use the same key to perform this function, an asymmetric encryption algorithm, on the other hand, uses one key to encrypt the data and another to decrypt it. In asymmetric systems, the key used for encryption, also known as the public key, can be freely shared with other users. On the other hand, the key used for decryption is private and must be kept secret.

For example, if Alice sends Bob a message protected by symmetric encryption, she needs to provide Bob with the same key she used to encrypt it so that he can read the message. This means that if an attacker intercepts it, he will be able to access the encrypted information.

However, if Alice uses the asymmetric method instead, she encrypts the message with Bob's public key, so Bob can decrypt it with his private key. Thus, asymmetric encryption provides a higher level of security because even if someone intercepts your messages and finds the public key, they will not be able to do anything with it.


Key length

Another functional difference between symmetric and asymmetric encryption relates to the length of the keys, which are measured in bits and are directly related to the security level of each algorithm.

In symmetric systems, the keys are selected randomly, and their generally accepted length varies between 128 and 256 bits, depending on the required level of security. In asymmetric encryption, there must be a mathematical connection between the public and private keys, that is, they are connected by a certain mathematical formula. For this reason, attackers can use this pattern to break the cipher, and asymmetric keys must be much longer to provide an equivalent level of security. The difference in key length is so significant that a 128-bit symmetric key and a 2048-bit asymmetric key provide approximately the same level of security.

 

Advantages and disadvantages

These two types of encryption have both advantages and disadvantages relative to each other. Symmetric encryption algorithms are much faster and require less computing power, but their main disadvantage is key distribution. Since the same key is used to encrypt and decrypt information, this key must be shared with everyone who needs access, which naturally creates certain risks (as described earlier).

In turn, asymmetric encryption solves the problem of key distribution by using public keys for encryption and private keys for decryption. The trade-off is that asymmetric systems are very slow compared to symmetric systems and require much more processing power due to key length.


Application options

Symmetric encryption

Due to its speed, symmetric encryption is widely used to protect information in many modern computer systems. For example, the Advanced Encryption Standard (AES) is used by the US government to encrypt classified information. AES replaced the older Data Encryption Standard (DES), which was developed in the 1970s as a symmetric encryption standard.


Asymmetric encryption

Asymmetric encryption can be applied to systems where many users may need to encrypt and decrypt messages or a packet of data, especially when speed and processing power are not a priority. A simple example of such a system is encrypted email, in which a public key can be used to encrypt messages and a private key to decrypt them.


Hybrid systems

In many applications, symmetric and asymmetric encryption are used together. A good example of such hybrid systems are the Security Sockets Layer (SSL) and Transport Layer Security (TLS) cryptographic protocols, which were developed to provide secure communications on the Internet. SSL protocols are currently considered insecure and are not recommended to be used. In turn, TLS protocols are considered secure and are widely used by all modern web browsers.


Using Cryptocurrency Encryption

Encryption methods are used by many crypto wallets as a way to provide an increased level of security to end users. Encryption algorithms are used when the user sets a password for their wallet file, which is used to access the software.

However, due to the fact that Bitcoin and other cryptocurrencies use a public and private key pair, there is a common misconception that blockchain systems use asymmetric encryption algorithms. However, as noted earlier, asymmetric encryption and digital signatures are the two main use cases for asymmetric cryptography (public key cryptography).

Consequently, not all digital signature systems use encryption, even if they provide public and private keys. In fact, a message can be digitally signed without using a cipher. RSA is one example of an algorithm that can be used to sign encrypted messages, but the digital signature algorithm used in Bitcoin (called ECDSA) does not have encryption.


Conclusion

Both symmetric and asymmetric encryption play an important role in ensuring the security of sensitive information and communications in today's digital world. Both ciphers can be useful, because each of them has its own advantages and disadvantages, so they are used in different cases. As cryptography as a science continues to evolve to protect against newer and more serious threats, symmetric and asymmetric cryptographic systems will always be relevant to computer security.