QTS_Unit3_Question2


There are many types of encryption in the world today, the popular ones are symmetric encryption, asymmetric encryption, and hybrid encryption.

Symmetric encryption is a form of encryption where the sender and receiver use the same key to encrypt and decrypt.

For example Caesar cipher.

It’s simply a type of substitution cipher, i.e., each letter of a given text is replaced by a letter some fixed number of positions down the alphabet.

For example, in the image below, we choose the key k = 3, the message is transmitted from the leader to the soldier that the enemy cannot read. When the soldier receives, he will use the key k = 3 to decrypt to know the plaintext of the message.
Here’s how to encode from history, today, the encryption can be represented using modular arithmetic by first transforming the letters into numbers, according to the scheme, A = 0, B = 1,…, Z = 25. Encryption of a letter by a shift n can be described mathematically as C=(P+k)mod26, where P is plaintext, k is key and C is Cyphertext.

In addition to Caesar cipher, modern symmetric ciphers also have other types such as block cipher, data cipher.
To increase security, we can use asymmetric encryption such as RSA encryption, Elgamal encryption,… . However, using asymmetric encryption for large amounts of data easily consumes the computer’s memory space. So today, asymmetric encryption is often applied in creating digital signatures and certificates to ensure the integrity of data.

Any encryption has advantages and disadvantages, so depending on the level of security and usage needs, we can choose encryption options to ensure information security and save computer space.

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