Please note that all my notes are referenced from my college notes. As a result, you might find them a little confusing in terms of their order. However, this is intentional to maintain consistency with the notes provided by the college.
This is a cryptographic key exchange algorithm that is used to securely trasmit a shared secret key between two parties over a insecure channel This is not a cipher
Humans have two basic needs when we take about communication. One is the need to communicate selectively, to communicate and share information. These two basic needs while communicating gave rise to coding and encrypting the messages in such a way that only intended people could have access to the information.
A Cipher is a algorithm for performing encryption and decryption - a series of well defined steps that can be followed as a procedure
Cryptography is the practice and study of techniques for secure communications between two parties
Here the units of the plaintext are rearranged or shuffled without changing the actual letters themselves using a key
In cryptography, a substitution cipher is a method of encrypting in which units of plaintext are replaced with the ciphertext, in a defined manner, with the help of a key; the "units" may be single letters (the most common), pairs of letters, triplets of letters, mixtures of the above, and so forth. The receiver deciphers the text by performing the inverse substitution process to extract the original message.