Cryptography is the practice of securing communication through the use of mathematical algorithms and protocols that convert plain text messages into a coded or encrypted format that can only be decoded by authorized parties. The goal of cryptography is to ensure that a message is not read or altered by unauthorized individuals or entities.

Cryptography is used in a wide range of applications, including online transactions, data storage, and secure communications between individuals or organizations. In online transactions, cryptography is used to ensure that sensitive information such as credit card numbers and personal identification information is transmitted securely.

One of the most commonly used cryptographic techniques is public key cryptography, also known as asymmetric cryptography. This technique involves the use of two different keys - a public key that can be shared with anyone and a private key that is kept secret. Messages are encrypted with the public key, but can only be decrypted with the private key, which is known only to the intended recipient.

Another common cryptographic technique is symmetric cryptography, in which the same key is used for both encryption and decryption. While this technique is less secure than public key cryptography, it is often used for encrypting large amounts of data.

Cryptography like a secret code that helps people keep their messages safe from anyone who shouldn't see them. Just like how you might use a secret code with your parents or friends to keep your messages secret from anyone else, cryptography uses special math tricks and computer programs to make sure that only the people you want to see your messages can understand them. It helps keep your important information, like your bank account number, safe when you're using your computer or phone.

Secure Online Transactions: Cryptography is used to secure online transactions, such as credit card payments, by encrypting the data exchanged between the customer's computer and the merchant's server. This helps ensure that sensitive information, such as credit card numbers and personal identification information, is transmitted securely and cannot be intercepted by unauthorized third parties.

Messaging Apps: Messaging apps like WhatsApp and Signal use cryptography to secure messages sent between users. Messages are encrypted on the sender's device and can only be decrypted by the intended recipient, ensuring that only the two parties can read the messages.

Passwords: Passwords are often encrypted using cryptographic techniques to ensure that they cannot be easily deciphered by hackers or other unauthorized individuals. When a user enters their password on a website or application, it is typically encrypted and stored in a database using a hashing algorithm, which makes it difficult for attackers to obtain the original password.