Symmetric key cryptography, or symmetric encryption, is a type of encryption system used to protect information. It relies on a single key that is shared between two or more users. The same key is used to both encrypt and decrypt any data or messages. This type of encoding has been increasingly used for its ability to facilitate secret communications between militaries or governments. In addition, symmetric key algorithms are now found in various types of computer systems for data security.
In a symmetric encryption scheme, plaintext messages or data are encrypted using an encryption algorithm known as a cipher. This cipher takes the input of the plaintext and produces an output of a ciphertext. The only way a person can read the information contained in the ciphertext is by using the corresponding key to decrypt it. This process is used to convert the ciphertext back to plaintext.
Security of symmetric encryption systems is dependent upon how hard it is to guess the correct key using a brute force approach. A longer key length improves the difficulty of cracking the encryption. For instance, a 128-bit key would take billions of years to crack with standard computer hardware. Keys that are at least 256-bits in length are the most secure and are resistant to quantum computer brute force attacks.
The two major types of symmetric encryption systems today are based on either block or stream ciphers. Stream ciphers encrypt messages in increments of 1-bit, while block ciphers group data into predetermined sized blocks and use the corresponding key and encryption algorithm to encrypt each block.
Symmetric key cryptography is different from asymmetric encryption, which is the major application of public key cryptography. Asymmetric encryption algorithms use two separate keys, one of which can be shared publicly and the other must be kept private. Asymmetric algorithms are more complex and slower than symmetric key algorithms.
Symmetric encryption algorithms are used for enhancing user privacy and data security in many modern computer systems. An example of this is the Advanced Encryption Standard (AES) which can be implemented in both software and directly in computer hardware. AES 256 is a variant of AES with a 256-bit key length.
The major disadvantage of symmetric key cryptography is the inherent problem of needing to safely and securely transmit the keys used to encrypt and decrypt data. This can be a major difficulty unless the keys are shared over a secure connection. As such, many web protocols make use of a combination of symmetric and asymmetric encryption to establish secure connections. The Transport Layer Security (TLS) protocol is an example of such a system which is used to protect large portions of the internet.
Symmetric encryption holds many benefits, from its relative speed, simplicity and security. Its security can be scaled up by increasing key sizes. Today, symmetric encryption is used for a variety of applications, from securing internet traffic to protecting data stored on cloud servers. It is important to note that all types of computer encryption might have certain vulnerabilities due to improper implementation or programming errors. As such, when it comes to dealing with sensitive data, it is recommended that encryption algorithms are used in a safe and secure manner.
