Symmetric key encryption is known for being affordable and efficient, but is this really the most secure strategy to encrypt and protect your information? Let’s dive into the advantages and disadvantages of symmetric encryption, along with some common pitfalls you’ll want to avoid if you do choose this method.
Cryptography is the practice of using mathematics to transmit and store information safely from one source to another, without others getting access to the message in between sources. Originally, the cryptography technique was created in Caesar’s time, when he began using the Caesar cipher. There are two parts to this process, the encryption and decryption. The encryption portion requires a code used to change the original text, the decipher will have received the code instructions and can read the message. These codes are called keys, and it’s how data today is protected.
What is symmetric key encryption?
Symmetric encryption is a method of cryptography where a single key is responsible for encrypting and decrypting data. The involved parties share that key, password, or passphrase, and they can use it to decrypt or encrypt any messages they want. It’s part of the public key infrastructure (PKI) ecosystem in how it makes it possible to send secure communications across the insecure internet by converting plain text, or readable data, into unrecognizable ciphertext.
According to the Open Web Application Security Project (OWASP), some of the most common algorithms used for symmetric cryptography include the Data Encryption Standard (DES), which uses 56-bit keys, Triple DES, which applies the DES algorithm three times with different keys; and the Advanced Encryption Standard (AES), an algorithm which the United States National Institute of Standards and Technology recommends new applications use for securely storing and transferring data.
When is symmetric key encryption used?
Symmetric encryption is a faster and more efficient method of encryption. Because of this, symmetric encryption is used for encrypting databases and other large groups of data. It can also be used for coding small groups of data, though this is less likely due to the more secure option of asymmetric encryption.
Differences between symmetric and asymmetric encryption
While symmetric encryption uses one key to encrypt a text, asymmetric encryption uses two keys to encrypt data, making it more difficult to attack. Asymmetric Encryption is considered a newer method of encryption. How it works is a message will be encrypted using a public key and can only be decrypted using the private key provided by the creator. One downside to asymmetric encryption is the time required to do it. Because of this, normally only small bits of data use asymmetric encryption.
What are the benefits of symmetric key encryption?
Symmetric key ciphers, the algorithms used to perform encryption and decryption, appeal to organizations because they are inexpensive relative to the level of protection they offer. Authentication is built into symmetric cryptography cannot be decrypted with any symmetric key, but only with the key that was used to encrypt it. The IBM Knowledge Center notes that symmetric key ciphers are also smaller in size, minimizing the time delay when encrypting and decrypting data.
Another benefit is that symmetric encryption is far less resource-intensive than asymmetric encryption and is an incredibly efficient way to protect large volumes of data. This is especially enticing to large enterprises who encrypt data in massive scales, such as banks.
How to avoid common mistakes using symmetric keys
Symmetric encryption isn't perfect. The biggest challenge is actually keeping the valuable keys a secret, which can become particularly challenging when the key has to be moved so that encryption and decryption can occur in different places.
Keys in this method of cryptography live on forever, which means organizations must invest in logging and auditing of the keys over their lifecycle. It also means that if a symmetric key is lost, organizations can't recall it. Instead, they must encrypt and decrypt data with a different key after they recover the data in an unencrypted form.
Given the business costs associated with symmetric key loss, companies need to take great care in ensuring the involved parties securely exchange and store their keys. As discussed in the Venafi Knowledge Base, one solution is to enact a custodial system by which custodians obtain portions of the key from a hardware security module (HSM), or a physical computing device that manages keys. They secure those components and mail them to receiving entities, who form the complete key by entering their respective key fragments into the HSM. Successful entry of all components allows recipients to encrypt and decrypt data using the completed key.
Alternatively, a custodian might obtain a symmetric key wrapped with an asymmetric keystore. That custodian can then mail that keystore to a receiver, who uploads the keystore into the HSM. The module, in turn, unwraps the keystore, thereby enabling the receiver to encrypt and decrypt messages. Of course, this method has its limits. If a recipient always needs another key to encrypt the symmetric key, things could spiral out of control and lead to a never-ending cycle of keys depending on additional keys.
Another trap far too many organizations fall into is using a single key to encrypt all data. A word to the wise here: creating a shortcut for your developers is also creating a shortcut for cyber criminals!
Automating key management for symmetric key encryption
When all is said and done, organizations need a way to monitor their keys. This process could become resource-intensive, for if multiple parties need to establish their own secure communications channels with one another using symmetric encryption, for they will need their own keys per each channel. This is why switching to automation for key management is the only real solution. Remove human error and misuse from the equation, and watch your network become more efficient and secure before your eyes.
(This blog has been updated. It was originally posted by David Bisson on November 9th, 2017.)