Encryption is a method of converting plain text into cipher text. Using this method, security of data can be achieved effectively. An encrypted file can be decrypted if the user has the capability of accessing a secret key or password. In this context, unencrypted data is referred to as plain text where as encrypted data is referred to as cipher text.
Figure 7.1: Encryption process
The below written are the two major types of encryption,
1. The Symmetric encryption
2. The Asymmetric encryption.
1. Symmetric Encryption is defined below
Symmetric encryption is also called as private key or the secret key encryption. In this, only one secret key is needed for the encryption and decryption of the message. This key is shared by sender and recipient both. It is an easy process when compared to asymmetric encryption.
2. Asymmetric Encryption is defined below
Asymmetric encryption is also called as pubic key encryption. In this, two keys are required for encryption and decryption of a message that is a public key and a private key. Private key should be reserved secret for the security purposes while the other key should be shared by sender and recipient both. It is a complex and time consuming process when compared to symmetric encryption.
Public key Cryptography is defined below
Public key cryptography was invented by the Diffie and 1-lehman in year 1976. For this very reason, it is sometimes called as Diffie-Heliman encryption. Public key cryptography is also called as asymmetric cryptography. It is the form of cryptography in which the user has a pair of cryptographic keys such as public key and private key. The private-key is kept secret, whereas the public key is distributed broadly. A message or text data which is to be encrypted
with the public-key can be decrypted only by making use of the corresponding private key. For example, when Johny wants to send the secure message to Sunny, he uses Sunny’s public key to encrypt the message. Sunny then uses his own private key to decrypt it.
A public key cryptography/encryption comprises of the five elements stated below. They
(i) Text data/Message
(ii) Encryption algorithm
(iii) Public key and private key (iv) Cipher text/Unreadable text (v) Decryption algorithm.
(i) Text data/Message is described below:
This can be any input data, like text data or message. For instance, Johny is a user of the computer and wants to send his message, M=“Hello” securely to friend Sunny, who is also a user of the computer.
(ii) Encryption Algorithm is described below:
To encrypt the message, an encryption algorithm performs particular transformation on it. There are many encryption algorithms but the RSA public key encryption algorithm is mainly used to perform the particular transformations or calculations on the text data or the message.
For instance, Johny uses the public key of the Sunny and encrypted his message by using the RSA algorithm.
(iii) Public Key and Private Key are described below:
These pair of keys is used to encrypt and decrypt the desired message respectively. The private key is always kept undisclosed, whereas public key is broadly distributed.
For instance, Johny uses a public key of Sunny to encrypt his message, whereas Sunny uses his private key to decrypt Johny’s message as shown in the figure drawn below.
(iv) Cipher text/Unreadable Text described below:
Once the encryption is performed on the text data it is in unreadable format that is it cannot be read by the human beings.
For instance, Johny’s message has converted into the unreadable from so that nobody except Sunny can read his message, as he has the corresponding private key for that particular message.
(v) Decryption Algorithm is described below
A decryption algorithm takes the unreadable text and the corresponding key of it to original text. Thus, we can say that the decryption algorithm is the reverse of the encryption algorithm.
For instance, decryption algorithm takes the unreadable text of the Johny and also takes the Sunny’s private key to decrypt the message and convert the unreadable text into readable form that is original text sent by Johny. As shown in the below figure drawn below