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Table of contents
Components of Cryptosystem
Types of Cryptosystems
Symmetric Key Encryption
Asymmetric Key Encryption
Kerckhoff's Principle of Cryptosystem
Key Takeaways
Last Updated: Mar 27, 2024


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In today's world, privacy is a significant concern for everyone. No company wants their secrets to be leaked. Everyone uses WhatsApp nowadays. It is written 'end-to-end encrypted' when you start a chat if you ever notice. So what is the meaning of that? It means that the message you send is first encoded into Ciphertext, and then they are sent on the communication channel. And when the other person receives it, it again is deciphered to the message you typed. The system through which this operation is performed is called a cryptosystem. This article will discuss Cryptosystem, its components, and types.


A cryptosystem is a suite of cryptography algorithms needed to provide security services like encryption meant for confidentiality. A simple block diagram of a cryptosystem has been given below to understand the workflow better.


Here the sender wants to transfer some data securely such that no third party having access to the communication line can access the data. Before sending the data on the communication line, it is first fed to an encryption system. It produces a ciphertext form of the message and is then put on the transmission line. The ciphertext is such that it can be decoded only with the key that is used to encode it. The key acts like a password here. When the receiver receives the ciphertext, it is fed to the decryption system, which decodes the message using the key. When a third party tries to hijack the message, they get a ciphertext that will be of no use without the key. In this way, the Cryptosystem assists the transfer of message signals securely. The process to convert the message into an encoded form is called encryption, and to derive the message back from its encoded form is called decryption.

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Components of Cryptosystem

The different components of a cryptosystem are as follows:

  1. Plaintext: It is the data that needs protection during transmission.
  2. Encryption Algorithm: This mathematical algorithm takes the Plaintext as input and produces an encoded plaintext form and an encryption key for that text.
  3. Ciphertext: This is the encoded form of the message. It is also known as the unreadable version.
  4. Decryption Algorithm: This mathematical algorithm takes the Ciphertext as its input and derives the original message using the decryption key.
  5. Encryption Key: This is a value known to the sender to encrypt the Plaintext into Ciphertext.
  6. Decryption Key: This is a value known to the receiver used to decrypt the Ciphertext to derive the Plaintext.

Types of Cryptosystems

Based on how encryption-decryption is performed, cryptosystems can be classified into two types:

  1. Symmetric Key Encryption
  2. Asymmetric Key Encryption

Symmetric Key Encryption

It is a type of encryption where only one key is used to encrypt and decrypt the Plaintext. This means the encryption key and decryption key are similar in Symmetric Key Encryption. The sender and receiver must communicate to share the key for the decryption process. Symmetric encryption is an older encryption method. It is faster and more efficient than asymmetric encryption because asymmetric encryption experiences performance issues due to data size and heavy CPU usage. Due to its better performance, Symmetric Encryption is used in encrypting large amounts of data like a database. Some examples of symmetric Encryption are Payment applications, card transactions, etc. 

Some Symmetric Encryption algorithms are:

  • AES (Advanced Encryption Standard)
  • DES (Data Encryption Standard)
  • RC4 (Rivest Cipher 4)

Asymmetric Key Encryption

This type of encryption uses two keys for encryption and decryption, respectively. The two keys, however, are mathematically related. The key used for encryption is a public key, and the key used for decryption is a private key. Asymmetric Key Encryption is also called public-key encryption. The public key is open to everyone, which means anyone can encrypt the data using it. But the private key is kept secret so that only authorized persons can access the encrypted data. Asymmetric encryption can be used to authenticate parties, verify data integrity, symmetric exchange keys, etc. If you see right now on your browser's address bar, you will see a lock icon. This lock icon means you are connected to a website that uses SSL/TLS certificates and the secure TLS protocol. This uses asymmetric key encryption to verify the identity of the server. Once the verification is done, the webserver switches to symmetric encryption for the rest of the session. Asymmetric encryption is more secure than symmetric encryption. 

Some standard asymmetric encryption algorithms are:

  • RSA
  • Diffie-Hellman
  • ECC

Kerckhoff's Principle of Cryptosystem

In the 19th century, Auguste Kerckhoff, a Dutch cryptographer, gave some design principles for a good cryptosystem. Kerckhoff believed that a cryptographic system must be secure even when everything about the system is public knowledge, except the key. 

The six design principles given by Kerckhoff are:

  1. The system must be indecipherable practically, if not mathematically.
  2. If it falls into enemy hands, it should not be a problem, i.e., there should be no secrecy.
  3. It must be possible to communicate and remember the key without using written notes, and correspondence must be able to change or modify it at will.
  4. The encoded information must be transmissible by even insecure channels such as the telegraph.
  5. The encryption system must be portable and operable by a single individual.
  6. The system must be easy to use, requiring minimal or no knowledge of a long set of operating rules, and it must not put the operator under mental strain.

Most of the above-stated rules have become outdated due to technological advancement and increased operating speed. However, the second hypothesis is critical in today's world and is known as Kerckoff's principle.

Also read - active and passive attacks


  1. Which Cryptosystem is faster, Symmetric or Asymmetric?
    Symmetric Cryptosystem is faster than Asymmetric Cryptosystem.
  2. Which Cryptosystem is more secure, Symmetric, or Asymmetric?
    Asymmetric Cryptosystem is more secure than symmetric Cryptosystem.
  3. RSA algorithm is the algorithm for Symmetric or Asymmetric Cryptosystem?
    RSA algorithm is an asymmetric cryptosystem algorithm.
  4. What are encryption keys and decryption keys?
    The encryption key is used to encrypt the Plaintext, and the decryption key is used to decrypt the Ciphertext.
  5. Which Cryptosystem is used to establish a secure connection with a third party?
    Asymmetric Cryptosystem is used for this purpose.

Key Takeaways

In this article, we have extensively discussed the cryptosystem topic. We have discussed the components and the types of Cryptosystem. We have also discussed Kerckhoffs' principle.

We hope that this blog has helped you enhance your knowledge regarding cryptosystems and if you would like to learn more, check out our articles.

Recommended Readings:

  1. Difference between Public Key and Private Key
  2. Cyber attacks & their types
  3. Cyber Security and Cyber Crime
  4. Cyber Security Challenges
  5. Active and Passive Attacks
  6. Active Attack and Passive Attack

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