Cyber Security

Types of Encryption: Symmetric or Asymmetric? RSA or AES?

If you’re looking to encrypt data to protect it, you might find there are different encryption methods and encryption algorithms to pick from. From RSA to AES, your pick should be informed by context.

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What is Data Encryption?

Data Encryption is a process that can be as easy as flipping on a switch if you know what you’re looking to achieve. Let’s recap the basics of this data security asset. To encrypt data is to take a piece of information, and translate it into another piece of unrecognizable information. This end product is called a ciphertext.

To get a ciphertext, you run the information that is to be encrypted through an encryption algorithm. This algorithm takes the original information and, based on randomized rules, transforms the information into a new, undecipherable piece of data. Think of it as a ‘translation’. What the encryption algorithm does is create a new language, and hides sensitive data by transforming it into this secret code, which you can only decrypt and turn back to plaintext if you know the rules, or what’s called a key.

The key represents the mathematical steps the algorithm took to convert your text from “Hello World” into “XJtg920kl#aJFJ”%*¨*FK”. Without it, you can’t decrypt the data, and thus it is protected from unauthorized access.But, there are many different types of encryption algorithms and methods to pick from, so how do you know which one is the safest pick for your cybersecurity needs? Let’s begin with the most basic distinction: symmetric versus asymmetric encryption.

Symmetric versus Asymmetric

Encryption types can be easily divided into these two categories: symmetric encryption, or single-key encryption, and asymmetric encryption, or public-key encryption.

Symmetric Encryption

In symmetric encryption, there is only one key, and all parties involved use the same key to encrypt and decrypt information. By using a single key, the process is straightforward, as per the following example: you encrypt an email with a unique key, send that email to your friend Tom, and he will use the same symmetric-key to unlock/decrypt the email.

symmetric encryption

The perks of symmetric encryption are its faster performance and low resource consumption, but it is inherently older and less secure than its counterpart. The reason is simple: if you scale your encryption to a company-wide scale, it means you’re putting all your trust into a single key you will need to share around a lot.

For this reason, Symmetric encryption is great when working with sensitive data in bulk, or encryption tasks that intend to permanently want to hide information without the need for decryption. For example, when you activate BitLocker on a Windows computer to encrypt all hard drives. By unlocking the PC with his/her passcode, the user will decrypt data without risk of exposing its secret encryption key. Another example are VPNs, which encrypt your network traffic with a local key and don’t have the need to share that outside of your own use.

Asymmetric Encryption

Asymmetric encryption, on the other hand, was created to solve the inherent issue of symmetric encryption: the need of sharing a single encryption key around that is used both for encrypting and decrypting data. 

asymmetric encryption

This newer and safer method utilizes two keys for its encryption process, the public key, used for encryption, and the private key used for decryption. These keys are related, connected, and work in the following way:

A public key is available for anyone who needs to encrypt a piece of information. This key doesn’t work for the decryption process. A user needs to have a secondary key, the private key, to decrypt this information. This way, the private key is only held by the actor who decrypts the information, without sacrificing security as you scale security.

A good example is email encryption. With asymmetric encryption, anyone can use your public key to send you an encrypted email that you only can decipher using your private key. 

Naturally, asymmetric is a more advanced encryption standard and thus is slower and resource consuming. Due to this, it is usually utilized in smaller transactions, usually to establish safe communication channels, or authenticating users.

Common Symmetric Encryption Algorithms

AES or Advanced Encryption System

AES is one of the most common symmetric encryption algorithms used today, developed as a replacement to the outdated DES (Data Encryption Standard), cracked by security researchers back in 2005. This new algorithm sought to solve its predecessor’s main weakness, a short encryption key length vulnerable to brute force.

AES encrypts information in a single block (block cipher), and does so one block at a time in what is called ’rounds’. Data is initially converted into blocks, and then these are encrypted with the key in different rounds depending on key size: 14 rounds for 256-bits, 12 rounds for 192-bits, and 10 rounds for 128-bits. The process involves a series of data manipulation and mixing steps that are done each round: substitution, transposition, mixing, column mix, sub bytes.

Why is AES one of the most frequently used algorithms? AES is fast, with a variable key length option that gives it extra security. It is ideal when handling large amounts of encrypted data.

Blowfish and TwoFish

Blowfish was another symmetric successor to DES, designed as a block cipher like AES but with a key length that goes from 32 bits to 448 bits. It was designed as a public tool, not licensed and free. This initial version was upgraded to TwoFish, an advanced version of the latter, which utilizes a block size of 128-bits, extendable up to 256-bits.

The main difference with other encryption algorithms is that it utilizes 16 rounds of encryption, independently of the key or data size. The main attractive of TwoFish is its flexibility in performance, giving you total control of the encryption speed.

The main reason why TwoFish is not considered the top symmetric algorithm is that AES gained recognition and was quickly adopted as a standard by manufacturers, meaning it had the upper technical edge.

3DES or Triple Data Encryption Standard

Finally, the direct successor to DES is 3DES, or Triple Des. This symmetric algorithm is an advanced form of the deprecated DES algorithm that uses a 56-bit key to encrypt blocks of data. Its concept is simple: it applies DES three times to each block of information, tripling the 56-bit key into a 168-bit one.

Due to applying the same process thrice, 3DES is slower than its more modern counterparts. Furthermore, by using small blocks of data, the risk of decryption by brute force is higher.

Despite its slower speeds and generally outdated status when compared to AES, it is still widely utilized in financial services to encrypt ATM PINs and UNIX passwords.

Common Asymmetric Encryption Algorithms

RSA or RivestShamirAdleman

Considered a staple of asymmetric encryption. Designed by the engineers that gave it its name in 1977, RSA uses the factorization of the product of two prime numbers to deliver encryption of 1024-bits and up to 2048-bit key length. According to research conducted in 2010, you would need 1500 years of computational power to crack its smaller 768-bit version!

However, this means that it is a slower encryption algorithm. Since it requires two different keys of incredible length, the encryption and decryption process is slow, but the level of security it provides for sensitive information is incomparable.

Since its speed isn’t convenient for processing large amounts of data, RSA encryption is mostly used in digital signatures, email encryption, SSL/TLS certificates, and browsers.

ECC or Elliptic Curve Cryptography

This method was originally pitched in 1985 by Neal Koblitz and Victor S. Miller, only to be implemented years later in 2004. ECC uses a fairly more difficult mathematical operation based on elliptic curves on a finite field, in what is called the Elliptic-curve Diffie–Hellman.

With ECC you have a curve, defined by a math function, a starting point (A), and an ending point (Z) in the curve. The key is that to get to Z, you have done a series of “hops”, or multiplications that resulted in Z. This amount of hops is the private key.

ECC elliptic curve cryptography
Randomized calculations can result in any type of arrangement in the curve.

Even if you have the starting and ending point (public key), and the curve, it is nearly impossible to crack the private key. This is because ECC is what is called a “trapdoor”, or a mathematical operation that is easy and quick to complete, but extremely difficult to reverse.

ECC, or ECDH, a mathematical formula is of such strength that it can match a 1024-bit key system with security with a 164-bit key. In its highest setting, 512-bits, ECC can achieve a comparable level of security of a 15360-bit RSA key!

To paint a picture, RSA 2048-bit keys are the banking standard, yet 521-bit ECC delivers the equivalent of a 15360-bit RSA key. 

Considering the aforementioned facts, ECC is considered the future of encryption. It’s asymmetric, yet it is able to provide a security level of 256 bits at a maximum key length of 521 bits, which ensures fast encryption speeds with a high complexity of decryption to ensure sensitive data stays safe.

ECC is also extremely attractive for mobile, where processing power is low and data transfers are high. The low-cost, low-impact, high-security combination makes it the ideal standard for protecting sensitive mobiles and apps.

Takeaways

Encryption can be an intimidating endeavor. Data is everywhere, and you must consider it on all levels: data at rest, data in motion, who and where need to access this information, how it is transmitted, and what types of interactions you have involving sensitive information that must be encrypted.

You could be encrypting your enterprise’s communications, web browser information, e-commerce transactions, your company’s database, hard drives, or customer and user data. Taking the first step might seem difficult, but it is necessary to document all data interactions and make a plan. This way, you’ll understand what types of encryption you’ll need.

Fortunately, there are many straightforward encryption tools that are already at your disposal, ready to be activated quickly as you figure out the extent of your data security protocols. FileVault on macOS comes integrated and ready to encrypt your Mac computers with AES; whereas Microsoft boasts BitLocker native encryption, capable of full disk encryption with AES and AES-XTS.

About the author

Nicolas Poggi

Nicolas Poggi is the head of mobile research at Prey, Inc., provider of the open source Prey Anti-Theft software protecting eight million mobile devices. Nic’s work explores technology innovations within the mobile marketplace, and their impact upon security. Nic also serves as Prey’s communications manager, overseeing the company’s brand and content creation. Nic is a technology and contemporary culture journalist and author, and before joining Prey held positions as head of indie coverage at TheGameFanatics, and as FM radio host and interviewer at IndieAir.