What is a Cipher? [Everything You Need to Know]

Keelan Balderson
Keelan Balderson

Updated · Sep 07, 2022

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If you’ve ever wondered what a cipher is or what exactly it does in the context of cryptography and cryptology, then you’re in the right place.

This article explains encryption and decryption, different types of historical and modern ciphers, and how we come across them daily.

Are you ready to learn something new? We’ll dive straight in:

What Is a Cipher?

A cipher is an algorithm for encrypting and decrypting data. In the traditional sense, it’s a method for concealing a secret message, one that only the sender and the receiver know how to decipher and understand—or that’s the goal.

To help define cipher methods, a primitive example simply involves substituting the regular alphabet with different characters, e.g., replacing each letter in a short message with the third one along in the alphabet.

Continuing this model, “meet me tomorrow” would become “phhx ph xrpruurz.” This could also be perceived as a code, though traditionally, cryptographic ciphers are defined differently from secret codes, which function by complex substitution. Users will have a codebook that outlines the relationship between random strings of numbers or characters and the words or phrases that are hidden.

Of course, our example can easily be cracked, illustrating why mathematicians and computers are the ones that develop and implement ciphers today. Advanced ones are used every day to secure computer data sent over networks.

Modern cryptography employs complex mathematical equations, or algorithms, along with secret keys, not codebooks. This form of encryption and decryption secures digital data and facilitates anonymous communication and authentication. For example, authentication for signing into an online account.

How Do Ciphers Work?

When using a cipher, the original message or data (such as a password) is called plaintext. This is the ordinary readable text before it’s encrypted or after it’s decrypted.

So what then is ciphertext? When the message or data is encrypted, its cipher language is called ciphertext.

It holds all the information as the original, yet it is not discernible by humans or, for the most part, computers. To decrypt it, you must know the method of encryption. In other words, ciphertext appears as gibberish until the process is reversed.

How to use a cipher?

Ciphers rely on keys, or as they are technically known, crypto variables. The encryption process varies based on the key that must be chosen beforehand. Without it, it is virtually impossible to decrypt the ciphertext back into the plaintext.

Ciphers can be grouped into a few different forms. Those based on a repeated stream of symbols are called stream ciphers, while the ones with fixed-size blocks of symbols are known as block ciphers.

If the same code is used for encrypting and decrypting, it works via a symmetric key cipher algorithm. If they require different codes, then it’s an asymmetric one.

For symmetric algorithms to work, both the sender and the recipient must know the key, with nobody else privy. Asymmetric ones present two different but closely linked keys where one might be public and the other private without the data being breached.

What Is a Cipher Used For?

If we try to define cipher use today, we must first consider it comes in many different contexts. Ciphers mostly facilitate data security and private communications. A common protocol is Transport Layer Security (TLS), which provides secure communication over a computer network.

They are also used in smartphones, ATMs, television, and disk encryption.

Moreover, when browsing a secure website via SSL, which displays the HTTPS prefix in your address bar, namely a cipher is being used between the browser and the server in question.

As the name suggests, cryptocurrency also relies on cipher cryptography to secure transactions.

Types of Ciphers

There are many kinds of cipher security that have evolved over the years. Historical ones are now easy to crack, while their modern counterparts present a far tougher challenge, depending on how they operate and how complex their keys are.

Traditional Ciphers

These weren’t much different than our alphabetical example. They are also known as substitution or transposition ciphers. The latter could turn the phrase “food hog” into “HGOFDOO.”

In the early twentieth century, machines began to perform encryption and decryption. Though the results were much more sophisticated, they still relied on the alphabet, thus claimed as weak by today’s standards.

What is a cipher today?

In the modern world of block, stream, and key ciphers, the following terms are common:

DES

DES (Data Encryption Standard) is a symmetric key algorithm invented by IBM in the late 70s.

The plaintext is split in half, then a 64-bit plaintext and a 56-bit key are used to create a 64-bit ciphertext. So, the cipher key length for the encryption is 56 bits, while the block size is 64, with 8 bits not used at all.

Although it’s still in action, the 56-bit size makes it insecure for many modern applications. The next option has mostly replaced it.

AES

AES stands for Advanced Encryption Standard. This symmetric key algorithm was invented by Vincent Rijmen and Joan Daemen in 2001. It is now the default for wireless networks and is used by hardware and software alike.

It utilizes 128-bit plaintext and a 128-bit key, creating a 128-bit block. This is processed into 16 bytes of ciphertext. The key length can be 128 bits, 192 bits, or 256 bits. The higher the number, the stronger the encryption.

AES-256 is commonly referred to as military-grade encryption.

RSA

RSA is another cipher example. It is named after its creators Rivest, Shamir, and Adleman. It’s a public/private key asymmetric technique used mainly to transfer data over the internet.

For example:

  • A browser sends a public key to a website’s server and requests some data.
  • The server uses the user’s public key to encrypt the data and send it out.
  • The user’s browser performs the cipher decryption with its private key.

Because it’s asymmetric, even if a third party gets the public key, only the user’s browser can decrypt it.

Other common ciphers that use symmetric encryption include:

  • Blowfish
  • DES
  • 3DES
  • IDEA
  • Serpent
  • Twofish
  • RC6

To the list of asymmetric encryption ciphers can be added:

  • Diffie-Hellman
  • ElGamal
  • Elliptic Curve Cryptography

Code vs. Cipher

In common terms, a secret code is frequently used as a synonym for a cipher. However, they are not quite the same thing. Codes refer to simple messages that are changed and shortened in the process of hiding their meaning. For example, the Telegraph code is used to shorten long Telegrams. Similarly, a mafioso might have used the phrase “take out the trash” over the phone to mask a criminal act.

A cipher refers to the individual characters, groups of characters, or data bits themselves. It is part of a more complex encryption system, where the ciphertext is unrecognizable. A code can make sense, even if the meaning isn’t known. A cipher is perceived as gibberish.

Although there are exceptions, you can think of a code as human language and a cipher as computer encryption.

When it comes to cipher vs. encryption, it’s important to note that this actually isn’t a clash, as the former facilitates the latter. It’s the type of lock and key, not the descriptor for something that is locked.

Wrap Up

So there you have it. Now you know the answer to the question, “What is a cipher?”

Though, let’s try it one more time to make sure it sticks—a cipher is a complex encryption process that is used to replace and secure data when sent across computer systems, networks, and the internet. If you fired up your laptop today and found this article, you likely used a cipher at some point along the way.

We hope you found this helpful. However, if your thirst for knowledge still isn’t quenched, just refer to our handy collection of guides full of useful info.

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Keelan Balderson

Keelan Balderson

A qualified journalist and longtime web content writer, Keelan has a passion for exploring information and learning new things. If he's not writing or pushing his own brands, you'll find him watching pro wrestling or trying not to rant about politics online.

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