Symmetric algorithm, also known as symmetric encryption or secret key algorithm, is basically a cryptography method that involves one key being responsible for data encryption and decryption.
Parties involved in this exchange share that one key, passphrase, or password, and utilize it for decrypting or decrypting messages. Common symmetric algorithms include the DES or Data Encryption Standard, the Triple DES, and the AES or Advanced Encryption Standard.
Below is a brief refresher on symmetric algorithm to prepare you for your CompTIA Security+ SY0-501 certification exam.
Symmetric Algorithm at Work
The most basic example of how symmetric algorithm works involves substituting letters in the alphabet before a target letter for every alphabet in the message. For example, the message “gdkkn” might seem nonsensical if you’re not aware that the algorithm used for it is (x-1). But all involved parties in the exchange will easily understand it as “hello”.
Benefits and Drawbacks of Symmetric Algorithm
Organizations like using secret keys used for symmetric encryption since they’re inexpensive considering the level of protection they can offer. Authentication is already formed into symmetric cryptography in order that parties won’t be able to decrypt encrypted data without the specific symmetric key.
Because of this authentication method, encryption and decryption of data are also faster. However, symmetric algorithm is not all that perfect. For one, the keys used with symmetric encryption live on forever, meaning that organizations should invest in auditing and logging keys over their lifetime.
This likewise means that in the event that a key disappears, organizations won’t be able to recall it. They would need to encrypt and decrypt data using a different secret key after they recover their unencrypted data.
The Custodial Symmetric Key Exchange
Considering the costs involved in losing symmetric keys, organizations have to make certain that all parties involved exchange their key as securely as possible. A great strategy is using the custodial symmetric key exchange system wherein custodians get some parts of the key from a physical computing device used for managing keys or an HSM or hardware security module.
The custodians then secure the parts and send them to the recipients who then enter their corresponding key parts into the HSM in order to complete the key and in turn, data encryption and decryption.
Wrapping Symmetric Keys for Data Exchange
Custodians could likewise get a symmetric key that’s wrapped with a keystore that’s asymmetric and then send the keystore to the recipient, who will then put it into the HSM. In turn, the HSM will unwrap it and allow the recipient to encrypt and decrypt the data.
This method, however, comes with certain limits. For example, in the event that the recipient constantly requires an additional key for encrypting a symmetric key, there’s a chance that everything could get out of hand and result in an endless cycle of symmetric keys relying on other keys.
Ultimately, organizations must implement proper key management strategies to get around all the drawbacks of using secret keys. Because in the end, symmetric algorithms really work, provided that organizations can secure and monitor them effectively.