Symmetric and asymmetric encryption: A comparative analysis

Modern cryptography is divided into two main branches: symmetric cryptography and asymmetric cryptography. Symmetric encryption is often synonymous with symmetric cryptography, while asymmetric cryptography encompasses two fundamental applications: asymmetric encryption and digital signatures.

This classification can be represented as follows:

Symmetric key cryptography:

• Symmetric encryption

Asymmetric cryptography ( or public key):

• Asymmetric encryption
• Digital signatures ( with or without encryption )

In this article, we will focus on symmetric and asymmetric encryption algorithms.

Differences between symmetric and asymmetric encryption

Encryption algorithms are generally categorized into two types: symmetric and asymmetric. The fundamental distinction lies in the fact that symmetric algorithms use a single key, while asymmetric ones use two related but different keys. This seemingly simple difference entails significant functional variations between both methods and their applications.

Relationship between keys

In cryptography, encryption algorithms generate keys as sequences of secret bits to encode and decode information. The way these keys are used makes the difference between symmetric and asymmetric methods.

While symmetric algorithms use the same key for both operations, asymmetric ones employ one key for encryption and another for decryption. In asymmetric systems, the encryption key, known as the public key, can be shared freely. In contrast, the decryption key is private and must be kept secret.

For example, if Ana sends Carlos a message protected with symmetric encryption, she must provide him with the same key that she used to encrypt it. This implies that if an attacker intercepts the communication, they could access the encrypted information.

However, if Ana uses the asymmetric method, she encrypts the message with Carlos's public key, which he will decrypt with his private key. Thus, asymmetric encryption offers greater security, since even if someone intercepts the messages and obtains 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, measured in bits and directly linked to the level of security of each algorithm.

In symmetric systems, keys are selected randomly and their commonly accepted length varies between 128 and 256 bits, depending on the required level of security. In asymmetric encryption, there must be a mathematical relationship between the public and private keys, meaning they are linked by a specific mathematical formula. For this reason, attackers could use this pattern to break the encryption, 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 offer approximately the same level of security.

Advantages and disadvantages

These two types of encryption have advantages and disadvantages over each other. Symmetric algorithms are considerably faster and require less computing power, but their main drawback is key distribution. Since the same key is used for both encryption and decryption, it must be shared with everyone who needs access, which naturally creates certain risks (as mentioned earlier).

On its part, asymmetric encryption solves the key distribution problem by using public keys for encryption and private keys for decryption. The disadvantage is that asymmetric systems are significantly slower compared to symmetric ones and require much more processing power due to the length of the keys.

Practical Applications

Symmetric encryption

Due to its speed, symmetric encryption is widely used to protect information in numerous modern computer systems. For example, the United States government employs the Advanced Encryption Standard (AES) to encode classified information. AES replaced the older Data Encryption Standard (DES), developed in the 1970s as a symmetric encryption standard.

Asymmetric encryption

Asymmetric encryption can be applied in systems where multiple users need to encrypt and decrypt messages or data packets, especially when speed and processing power are not priorities. A simple example of this type of system is encrypted email, where a public key can be used to encode messages and a private key to decode them.

Hybrid systems

In numerous applications, symmetric and asymmetric encryption are combined. A notable example of these hybrid systems is the Transport Layer Security protocols (TLS), developed to provide secure communications over the Internet. Currently, TLS protocols are considered secure and are widely used by all modern web browsers.

Use of encryption in cryptocurrencies

Many cryptocurrency wallets implement encryption methods as a way to provide an additional level of security to end users. Encryption algorithms are employed when the user sets a password for their wallet file, which is used to access the software.

However, because Gate and other cryptocurrency platforms use a pair of public and private keys, there is a misconception that blockchain systems employ asymmetric encryption algorithms. Nevertheless, as mentioned earlier, asymmetric encryption and digital signatures are the two main applications of asymmetric cryptography (public key cryptography).

As a result, 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 encryption. RSA is an example of an algorithm that can be used to sign encrypted messages, but the digital signature algorithm used in Gate ( called ECDSA) does not incorporate encryption.

Final Thoughts

Both symmetric and asymmetric encryption play a crucial role in ensuring the security of information and confidential communications in today's digital world. Both types of encryption are useful, as each has its own advantages and disadvantages, making them applicable in different scenarios. As cryptography as a science continues to evolve to protect against more sophisticated and serious threats, symmetric and asymmetric cryptographic systems will remain relevant to computer security.