Page 51 - CITS - Computer Software Application -TT

COMPUTER SOFTWARE APPLICATION - CITS

he primary application of cryptography in electronic data transmission is the encryption and decryption of emails
and other plaintext messages. The most straightforward technique is the “secret key” or symmetric approach.
In this method, a secret key is employed to encrypt the data, and upon decryption, the secret key and the encoded
message are shared with the recipient. However, a significant problem arises from this process. If intercepted, a
third party could use the shared key to decipher and analyze the message.
To address this issue, cryptographers developed the asymmetric or “public key” approach. In this scheme, each
user possesses two keys: a private key and a public key. Before sending a message, the sender obtains the
recipient’s public key and uses it to encrypt the message. Since only the recipient has access to their corresponding
private key, they can decrypt the message.
This asymmetric approach resolves the security vulnerability of the secret key approach, ensuring that even if the
communication is intercepted, only the intended recipient possessing the private key can decipher the message.
Plain Text: Plain text is the original, unencrypted message or data that you want to protect or transmit securely.
It’s the human-readable form of the information that you can easily understand. For example, if you have a
message like “Hello, this is a secret message,” that would be the plain text.
Ciphertext: Ciphertext refers to the transformed and encrypted form of data that has undergone encryption using
cryptographic techniques. It is the result of applying an encryption algorithm to plaintext (original, readable data)
in order to secure it during transmission or storage. Ciphertext appears as a seemingly random and unreadable
sequence of characters, making it unintelligible without the appropriate decryption key or algorithm. The primary
purpose of ciphertext is to protect sensitive information from unauthorized access, ensuring its confidentiality and
integrity.

For instance, let’s employ the Caesar Cipher to encrypt a sentence. With a key of 7, the letter ‘a’ shifts to ‘h’.
Original Sentence: This is a plaintext.
Encrypted Sentence(Ciphertext): Aopz pz h wshpualea.
Purpose of cryptography

• The purpose of cryptography is to secure communication and data by converting information into a format that
is unintelligible to unauthorized individuals.
• This safeguards sensitive information during transmission and storage, preventing unauthorized access,
eavesdropping, and tampering.
• Cryptography also enables the verification of data authenticity and the authentication of users or entities in
digital transactions.

• Overall, cryptography plays a vital role in ensuring privacy, data integrity, and secure interactions in various
digital environments.
Cryptographic algorithms
Cryptographic algorithms, also referred to as ciphers, are essential components of cryptosystems that ensure
secure communication between computer systems, devices, and applications.
A cipher suite encompasses various algorithms: one for encryption, another for message authentication, and
yet another for key exchange. These processes are integrated into protocols and implemented through software
operating on operating systems and interconnected computer networks. This involves:

- Generating public and private keys for encrypting and decrypting data.
- Performing digital signatures and verification for authenticating messages.
- Executing key exchange mechanisms to establish secure communication channels.
Types of Cryptography
Symmetric key
Symmetric key cryptography involves a method where both the sender and recipient utilize a common shared key
for both encrypting and decrypting messages.

38

CITS : IT&ITES - Computer Software Application - Lesson 01-17