Symmetric cryptography uses symmetric-key algorithms for the encryption and decryption of data. An algorithm is a specific formula with a limited number of steps that contains instructions for solving a problem, and a symmetric-key algorithm is a specific formula that often uses the same cryptographic key for both encryption and decryption. To better understand how this works, it helps to have an understanding of how cryptography works in relation to technology.
For example, a computer that needs to transfer sensitive information may choose to encrypt the information, a process which alters it into a sort of code that would appear as a bunch of nonsense if anyone tried to read it. After the information is transferred to its desired location, a specific code deciphers the information into readable text. This process is known as decryption and the computer must have the right code to perform this process correctly. Banks that offer online services use a form of encryption to keep their customers’ information private and secure.
A mathematical formula known as a cryptographic algorithm is responsible for creating the code to encrypt the information and the code for deciphering it later on. A specific piece of information known as a cryptographic key tells the cryptographic algorithm how to encrypt and then decode the specific information it receives. The key only works with that particular algorithm and would be useless for deciphering code from a different algorithm.
When using symmetric cryptography, the algorithm uses the same cryptographic key for performing the encoding and decoding processes instead of using a separate key for each. The keys are usually identical or nearly identical with only one small change required to make each one work. Typically, only those who plan to use the key will know the password or other secret code, or phrase, needed to cause the key to start working. This allows two people to share information between themselves without worrying that someone else might intercept the code and read it.
Other terms used to describe the symmetric-key algorithms used in symmetric cryptography include secret-key cryptography, private-key cryptography, and one-key cryptography. Symmetric cryptography is normally used for sharing between two people or a small group instead of by large online networks like banks. An ATM machine, for example, may use symmetric cryptography and require the user to input a bank account number and personal identification number before it will let that person access his account.