Basics of Encryption and Decryption


In computing, encryption is the method by which plaintext or any other type of data is converted from a readable form to an encoded version that can only be decoded by another entity if they have access to a decryption key. Encryption is one of the most important methods for providing data security, especially for end-to-end protection of data transmitted across networks.

Encryption is widely used on the internet to protect user information being sent between a browser and a server, including passwords, payment information and other personal information that should be considered private. Organizations and individuals also commonly use encryption to protect sensitive data stored on computers, servers and mobile devices like phones or tablets.

Benefits of Encryption

The primary purpose of encryption is to protect the confidentiality of digital data stored on computer systems or transmitted via the internet or any other computer network. A number of organizations and standards bodies either recommend or require sensitive data to be encrypted in order to prevent unauthorized third parties or threat actors from accessing the data. For example, the Payment Card Industry Data Security Standard requires merchants to encrypt customers’ payment card data when it is both stored at rest and transmitted across public networks.

Modern encryption algorithms also play a vital role in the security assurance of IT systems and communications as they can provide not only confidentiality, but also the following key elements of security:-

  • Authentication: The origin of a message can be verified.
  • Integrity: Proof that the contents of a message have not been changed since it was sent.
  • Non-repudiation: The sender of a message cannot deny sending the message.

Types of Encryption

(1) Symmetric key / Private key

In symmetric-key schemes, the encryption and decryption keys are the same. Communicating parties must have the same key in order to achieve secure communication.

(2) Public key

In public-key encryption schemes, the encryption key is published for anyone to use and encrypt messages. However, only the receiving party has access to the decryption key that enables messages to be read, Public-key encryption was first described in a secret document in 1973;, before, then all encryption schemes were symmetric-key (also called private-key).


The conversion of encrypted data into its original form is called Decryption. It is generally a reverse process of encryption. It decodes the encrypted information so that an authorized user can only decrypt the data because decryption requires a secret key or password.

One of the reasons for implementing an encryption-decryption system is privacy. As information travels over the Internet, it is necessary to scrutinise the access from unauthorized organizations or individuals. Due to this, the data is encrypted to reduce data loss and theft. Few common items that are encrypted include text files, images, e-mail messages, user data and directories. The recipient of decryption receives a prompt or window in which a password can be entered to access the encrypted data. For decryption, the system extracts and converts the garbled data and transforms it into words and images that are easily understandable not only by a reader but also by a system. Decryption can be done manually or automatically. It may also be performed with a set of keys or passwords.

There are many methods of conventional cryptography, one of the most important and popular method is Hill cipher Encryption and Decryption, which generates the random Matrix and is essentially the power of security. Decryption requires inverse of the matrix in Hill cipher. Hence while decryption one problem arises that the Inverse of the matrix does not always exist. If the matrix is not invertible then the encrypted content cannot be decrypted. This drawback is completely eliminated in the modified Hill cipher algorithm. Also this method requires the cracker to find the inverse of many square matrices which is not computationally easy. So the modified Hill-Cipher method is both easy to implement and difficult to crack.

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