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Table of contents
1.
Introduction
2.
What is Ciphertext?
3.
Why is Ciphertext Used?
4.
Ciphertext Example
5.
Difference Between Ciphertext and Encryption
6.
Types of CipherText
6.1.
Classical Ciphers
6.1.1.
Substitution
6.1.2.
Transposition
6.2.
Modern Ciphers
6.2.1.
Public Key
6.3.
Private Key
7.
Uses of CipherText
8.
Email Ciphertext
9.
CipherText Attacks
9.1.
Known CipherText Attack
9.2.
Chosen Ciphertext Attack
9.3.
Cryptanalysis Attack
10.
Frequently Asked Questions
10.1.
Is Stream Cipher better than Block Cipher?
10.2.
What is the Caesar Cipher?
10.3.
Which Modern Cipher is the most commonly used Cipher?
11.
Conclusion
Last Updated: Apr 1, 2024
Easy

What is a CipherText?

Author Nidhi Kumari
1 upvote
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Ashwin Goyal
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Introduction

What comes to your mind when you hear the name JULIUS CAESAR? Yes, you guessed it right, he was a politician and general in the Roman Empire who declared himself dictator of the Roman Empire. There is one more interesting fact about him. Caesar was the first person in Roman history to be concerned with creating a system to secure vital information.

What is a Ciphertext?

One of the first known ciphers is the "Caesar Box" or "Caesar Cipher." It was created around 100 BC and used by Julius Caesar to send secret information to his generals. 

In this article, we will discuss what is ciphertext, types of ciphers, uses of ciphertext, ciphertext attacks and some examples of ciphertext.

What is Ciphertext?

To understand what ciphertext is, let’s start with a simple example.

Suppose you want to send a secret message to your friend “The password of my Coding Ninjas account is CODE STUDIO”.

To hide your message, you are using a technique of shifting letters. You are shifting the alphabet by three spaces in the forward(right) direction. Only you and your friend know the pattern.

Alphabets:     A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Shifted Text:  X Y Z A B C D E F G H I J K L M N O P Q R S T U V W

 

Secret Message: The password of my Coding Ninjas account is CODE STUDIO.

Changed Text:     Qeb mxpptloa lc jv Zlafkd Kfngxp xzzlrkq fp ZLAB PQRAFL.

This changed text is the Ciphertext.

Ciphertext, also known as "cipher", is encrypted text using an encryption technique to change plaintext. A plaintext message is an input into an encryption algorithm, which then processes the plaintext to create a ciphertext.

Anything that people can understand or relate to is considered plaintext.  Examples of plain text include a script, English phrases,  simple code etc.

The simplest ciphers replace one letter with another as directed by a list of substitutions known as a KEY. The only way to read ciphertext is to use a key to decrypt it and turn it into plaintext.

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Why is Ciphertext Used?

Ciphertext is used to ensure the confidentiality and security of information during transmission or storage. It is the encrypted form of plaintext, making it unintelligible to unauthorized parties without the decryption key.

Ciphertext Example

Ciphertext is the encrypted form of plaintext. For instance, if "HELLO" is the plaintext and it is encrypted using a cryptographic algorithm, the resulting ciphertext might look like "Uryyb".

Difference Between Ciphertext and Encryption

ParameterCiphertextEncryption
DefinitionEncrypted form of plaintextProcess of converting plaintext to ciphertext using an algorithm and a key
IntelligibilityNot intelligible without the decryption keyNot applicable (process)
UsabilityUsed for secure transmission/storageUsed to protect sensitive information
TransformabilityIt can be transformed back to plaintext using decryption keyNot applicable (process)
VisibilityVisible result of the encryption processNot applicable (process)
SecurityProvides confidentialityPart of the process to ensure security

Types of CipherText

After discussing what is ciphertext, we will now discuss the types of Ciphertext.

Types of CipherText

Classical Ciphers

Classical ciphers are those that were created before the computer. Any of these can be easily broken with a slow, outdated computer. Throughout history, up until the early stages of World War II, people used the Classical ciphers.

Substitution

While maintaining the original order, a substitution cipher replaces 

  • Single letters.
     
  • Pairs of letters.
     
  • Triplets of letters.
     
  • Any combination. 
     

There are two types of Substitution ciphers:

  1. Mono Alphabetic.
     
  2. Poly Alphabetic.

 

Mono Alphabetic: The entire plaintext message is encrypted using a single alphabet. 

For example, the entire message will have the same encryption if the letter N is encoded as the letter D.

Plain text: CODINNINJAS

Cipher text: CODIDDIDJAS

 

Poly Alphabetic: A more complex version that encrypts every bit, letter, or character block in a plaintext message using a mixed alphabet.

For example, the letter N might be encoded as the letter D for one portion of the message before being changed to E in another part of the message.

Plain text: CODINNINJAS

Cipher text: CODIDEIEJAS

 

Transposition

Transposition ciphers preserve the same letters but rearrange their order under a specified algorithm, unlike substitution ciphers that swap out letters for other letters.

For example, a message might be read horizontally but written vertically to create the ciphertext in a simple columnar transposition cipher.

Plain text: CODING NINJAS

Key: 43152

Transposition Ciphers

Cipher text: I D C  N O N I G J N X X A X S

Here, Xs are used as padding bits. Consider the situation when the length of plain text is not a multiple of the key length. In such cases, we use Padding bits.

Plain text: CODE STUDIO

Key length: 3

We will break the plaintext into a group of 3.

COD EST UDI OXX

Modern Ciphers

The secret to modern computer and communication security is modern ciphers. It directly manipulates letters and numbers, which are standard characters. It uses binary bit sequences to work. Moser ciphers' encryption and decryption process rely on keys(short strings or text).

Public Key

Public-key cryptography, also known as an asymmetric cipher, is an encryption technique that employs two keys—a public key and a private key—that are mathematically linked but not identical. The private key is used to decrypt, whereas the public key is used to encrypt data.

Public Key

Private Key

Both the receiver and the sender in this encryption need to have a pre-shared key. The shared key is used for encryption and decryption and is kept a secret from all other participants. The term "symmetric ciphers" is another name for this encryption.

Private Key

The two types of symmetric cipher are

  • Stream Cipher.
     
  • Block Cipher.
     

Stream Cipher: Stream ciphers deal with encrypting continuous streams of data. They use a pseudo-random digit stream, also known as a key stream, to apply an encryption method to plain text, bit by bit encrypting it. 

To learn more about Stream Ciphers, you can visit our article on Stream Ciphers.

Block Cipher: Blocks of data with a fixed size and measured in bits are the focus of block ciphers.  The entire blocks are encrypted one at a time using a symmetric key. The length of the block influences the strength of the key– the longer, the better.

To learn more about Stream Ciphers, you can visit our article on Block Ciphers.

Uses of CipherText

In our article What is CipherText; we will now discuss the uses of Ciphertext.

  • Symmetric ciphers are ciphers that are used to secure online communications. Network protocols use a variety of symmetric cyphers to encrypt messages.
     
  • When simplicity and speed are goals, stream ciphers work best. For example, secure wireless connections where the length of the plain text is unknown.
     
  • Governments and companies with virtual private networks that handle sensitive data often use block cyphers to protect the data.
     
  • To access the plain text contained within the encrypted data, one of the most secure encryption methods, AES encryption, requires the recipient of the ciphertext possess the proper key.
     
  • Protocols use asymmetric encryption to encrypt and verify endpoints.
     
  • Asymmetric cryptography is used by other protocols, such as secure shell and OpenPGP, to encrypt and verify endpoints and safely exchange the symmetric key

Email Ciphertext

  • Email ciphertext refers to the encrypted form of email content or attachments.
  • It ensures that email communication remains confidential and secure.
  • Encrypted emails can only be deciphered by authorized recipients with the appropriate decryption key.
  • Protects sensitive information from unauthorized access during transmission or storage.
  • Utilizes cryptographic algorithms and keys to convert plaintext emails into unintelligible ciphertext.

CipherText Attacks

In our article What is CipherText; we will now see the Ciphertext attacks.

It has become crucial to protect vital information against harmful actions like attacks. Let's discuss the different forms of CipherText attacks.

Known CipherText Attack

In this attack, the attacker gets access to a particular collection of ciphertext. However, this technique prevents the attacker from accessing the related plaintext or unencrypted data that is sent or stored.  This method can extract the encryption key used to encrypt the ciphertext. The attack is successful when the attackers can extract the appropriate plaintext from a given collection of ciphertext. It is also known as a Ciphertext-only attack.

Chosen Ciphertext Attack

The CCA wants to learn facts that will make the encryption technique less secure.

In a chosen ciphertext attack, the attacker can force the victim to decrypt any ciphertext and send back the results if they have access to the secret key. 

The attacker attempts to determine the victim's secret key by examining the victim's chosen ciphertext and the related plaintext they receive.

Cryptanalysis Attack

A related-key attack is any cryptanalysis in which the attacker can watch how a cypher behaves while using a variety of keys whose values they are initially unaware of. The attacker is aware of some mathematical connection between the keys, though.

The attacker wants to locate the keys on their own. Attacks are referred to be known related key attacks or chosen related key attacks depending on whether the attacker may modify the relation or not.

Frequently Asked Questions

Is Stream Cipher better than Block Cipher?

Unlike block ciphers, which encrypt entire blocks of data at once, stream ciphers only encrypt one piece of data at a time, making them faster and more effective. They are, therefore, more appropriate for low-resource devices.

What is the Caesar Cipher?

Caesar Cipher is a type of Substitution Cipher. Each letter in the plaintext is "shifted" a specified amount of places down the alphabet when using the Caesar cypher.  For example, with a shift of 1, A would become B, B would become C, etc., and the letter A in plaintext would be replaced by B.

Which Modern Cipher is the most commonly used Cipher?

Symmetric ciphers are the most commonly used ciphers. Online communications are typically secured using symmetric ciphers. They are also included in numerous other network protocols to be used for data transfers.

Conclusion

We discussed What is ciphertext, its types, examples, and ciphertext attacks. The idea behind ciphertext is relatively simple, and it offers an excellent approach to protecting the privacy of information.

We hope this blog has helped you. We recommend you visit our articles on different topics of Cryptography, such as

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