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Blog Encryption Unlocking the Mystery of Ciphertext: How to Decode Hidden Messages


june 19 2023


Table of Contents

What Is Ciphertext and How Does it Work?

Ciphertext is the output of the process of encrypting plaintext using an encryption algorithm. It is an unintelligible and scrambled message that is impossible to read without the appropriate decryption key. Ciphertext is often used in cryptography to protect sensitive data from unauthorized access. In this process, the plaintext is transformed into ciphertext using an encryption algorithm, and then the ciphertext can be safely transmitted over an insecure channel or stored in an unsecured location.  

What Are Ciphertext and Plaintext?

The ciphertext is the result of enciphering the plaintext using an algorithm called a cipher. The encrypted plaintext cannot be read by a person or computer without processing in accordance with the used cipher and decryption key.

Decryption, the reverse of encryption, is the process of turning ciphertext into readable plaintext. Cipher text should not be confused with code text, because the latter is the result of a code, not a cipher.

Plaintext – in cryptography, the source text is encrypted, or resulting from decryption. Can be read without additional processing.

Plaintext is often text written in one of the natural languages. To reduce the redundancy inherent in natural languages ​​and increase the performance of encryption, the text is usually compressed before encryption. Information stored in non-textual form is also called plain text. The main thing is that decryption is not required to use such information.

Ciphertext Example

The Caesar cipher, also known as the shift cipher, the Caesar code is one of the simplest and most widely known encryption methods. The cipher is named after the Roman general Gaius Julius Caesar, who used it for secret correspondence with his generals.

This is a type of substitution cipher in which each character in the plaintext is replaced by a character located some constant number of positions to the left or right of it in the alphabet. For example, in a cipher with a right shift of 3, A would be replaced by D, B would become D, and so on.

The Characteristics of Ciphertext

The cipher can be a combination of conventional characters or an algorithm for converting ordinary numbers and letters. The process of encrypting a message with a cipher is called encryption. The science of creating and using ciphers is called cryptography. Cryptanalysis is the science of methods for obtaining the original value of encrypted data.

An important parameter of any cipher is the key – a parameter of a cryptographic algorithm that ensures the choice of one transformation from a set of transformations possible for this algorithm. In modern ciphers, it is assumed that all the secrecy of a cryptographic algorithm is concentrated in the key, but not in the details of the algorithm itself. This is called the Kerckhoff principle.

Types of Ciphers

The basic principle of operation of any cipher lies in the processes of encryption and decryption. From one device, information is sent in encrypted form, and to another it is received and decrypted into the original plain text. Encryption of information requires the exchange of keys between participants.

Substitution Ciphers

In these types of ciphers, the character is changed to another. Additionally, groups can be changed by an equal number of letters or numbers. The method is easy to read even without a generated key.

For decryption substitution ciphers, frequency analysis will be required. For this, the number of characters in the ciphertext is counted. These numbers are then divided by the number of letters in the alphabet used in encryption. In the end, the received frequency of each letter is compared with the reference one.

Transposition Ciphers

With this type of encryption, the participant independently chooses the principle of permutation of letters or phrases. It can be a number or a direction of writing. To decrypt, you will need to know the key and the rule by which the characters in the sentence or text were replaced.

In transposition ciphers, each individual sentence can be written in reverse – backward. In the text, each individual word can be encrypted according to this principle, or the method can be combined with a simple placement of phrases or words. Transposition is used for tabular encoding. The original text is written vertically. For encryption, it is drawn horizontally or vice versa.

Polygraphic Ciphers

Polygraphic ciphers can be based on linear algebra and modular arithmetic. Their main advantage was supposed to be protected from frequency analysis. Such ciphers are not widely used, since they do not have sufficient resistance to cracking and they lack a description of the algorithms for generating large direct and inverse matrices.

Such types of ciphers are vulnerable to chosen-plaintext attacks because they use linear operations. A cryptanalyst who intercepts n^2 message character/ciphertext character pairs will be able to come up with a system of linear equations that is usually easy to solve. If it turns out that the system is unsolvable, then you just need to add a few more pairs of message characters/ciphertext characters.

Permutation Ciphers

Permutation Ciphers are an encryption method in which elements of the original plaintext are swapped. Text elements can be single characters, pairs of letters, triples of letters, a combination of these cases, and so on. Typical examples of permutation are anagrams. In classical cryptography, Permutation Ciphers can be divided into two classes:

  • Single Simple Permutation Ciphers – when encrypting, plaintext characters are moved from their original positions to new ones once.


  • Multiple Complex Permutation Ciphers – during encryption, plaintext characters move from their original positions to new ones several times.

Private-Key Cryptography

Secret key ciphers or private key cryptography include encryption systems using a pre-designed key. It should be known only to persons conducting private correspondence with each other. For the prompt conversion of the information received, the key must already be on hand or indicated in the message itself.

As a result, users first need to obtain the key itself, and then proceed with its help to decrypt the received message. The action to create an encrypted message for the sender is performed in reverse order.

Private key cryptography is also referred to as symmetric encryption, where the same private key is used for both encryption and decryption. Symmetric key ciphers operating on fixed-length groups of bits, called blocks, are called block ciphers. Block ciphers are elementary components in the design of many cryptographic protocols and are widely used in data exchange protocols.

Public-Key Cryptography

The difference between asymmetric encryption and symmetric encryption is in the keys. The public key cipher often requires two keys for each participant. The public key is used for encryption. It is freely available. A second key is required to decrypt the message. It is private and there is no need to transfer it. Decrypting information without the private key will not work.


Cryptanalysis is the science of methods for decrypting encrypted text without a key intended for this, as well as the process of such decryption.

In most cases, cryptanalysis means finding out the key; cryptanalysis also includes methods for detecting the vulnerability of cryptographic algorithms or protocols.

An attempt to break a particular cipher using cryptanalysis methods is called a cryptographic attack on that cipher. A cryptographic attack that breaks a cipher is called a “crack” or “crack” of the cipher.

Initially, cryptanalysis methods were based on the linguistic patterns of natural text and were implemented using only pencil and paper. Over time, the role of purely mathematical methods in cryptanalysis is growing, for the implementation of which specialized cryptanalytic computers are used.

Uses of Ciphertext

Modern ciphertext forms a separate scientific direction at the intersection of mathematics and computer science – works in this area are published in scientific journals, and regular conferences are organized. The practical application of encryption has become an integral part of the life of modern society – it is used in industries such as e-commerce, electronic document management and digital signatures, telecommunications, and others.

Nowadays, ciphertexts are formed using well-known open encryption algorithms that involve the use of computational tools. There are more than a dozen proven encryption algorithms that, when using a key of sufficient length and the correct implementation of the algorithm, are cryptographically secure.

Email Ciphertext

Two standards are currently widely used for mail encryption: S / MIME using a public key infrastructure and OpenPGP using certificates with a trust scheme grouped around the user.

Previously, there were also MOSS and PEM standards, but, due to incompatibility with each other and inconvenience of use, they did not take root.

The S/MIME and OpenPGP standards provide three types of security: mutability, irrevocable signature, and confidentiality. Additionally, S/MIME version 3 allows secure handshaking. At the same time, a letter receipt can be generated successfully only if the letter has reached the recipient unchanged.

Both standards use symmetric cryptographic algorithms to encrypt the message body, and the symmetric key is encrypted using the recipient’s public key. If the letter is addressed to a group of people, then the symmetric key is encrypted in turn by each of the recipient’s public keys (and sometimes, for convenience, by the sender’s public key so that he can read the letter sent by him).

Ciphertext Attacks

Ciphertext attacks are the most explored methods of cryptanalysis. It is assumed that the cryptanalyst knows only a set of ciphertexts, the goal is to obtain as many plaintexts as possible corresponding to the available ciphertexts, or even better – the key used in encryption. Ciphertexts can be obtained by simply intercepting messages over open communication channels.

One of the most successful attacks of this type is an attack on WEP, a security algorithm for Wi-Fi networks. This attack requires interception and analysis of the transmitted data. All attacks are based on the shortcomings of the RC4 algorithm used for encryption in WEP, as well as on the use of weak initialization vectors.


Ciphertext is a crucial aspect of modern cryptography that allows for secure communication and data privacy. By transforming plaintext into a scrambled, unintelligible message, ciphertext makes it difficult for unauthorized parties to access sensitive information. Helenix develops cryptographic solutions for a variety of business needs. You can learn more about our competencies in the Custom Development section of our website.


A ciphertext-only attack is a type of attack where an adversary tries to decrypt encrypted messages without any knowledge of the encryption key or the plaintext.

A cipher is an algorithm used to encrypt plaintext into ciphertext, while ciphertext is the resulting scrambled and unintelligible message that has been encrypted using a cipher.

Encryption is the process of transforming plaintext into ciphertext using a cipher, while ciphertext is the resulting scrambled and unintelligible message that has been encrypted using encryption.

Ciphertext is generated by using an encryption algorithm to transform plaintext into a scrambled message. The process is typically performed by software or hardware designed to implement the chosen encryption algorithm.