Nowadays we can say that cryptography is part of computer science due to the explicit formulas, algebra and/or calculation schemes. As a science, cryptography plays the role of securing communication between two parties. A large part of it is encryption and decryption but in the past few years its range has been dramatically expanded. In a nutshell, if it is de/encryption then the information gets "encrypted" and then "decrypted" by knowing a secret "key" or password.

Like I said, cryptography's utilization has been expanded and it isn't uncommon at all to find authentication, digital signature verification and such. Basically this way the receiver is "verified" to determine if s/he is indeed eligible to view the secured information. This is another usage of cryptography that plays a huge role in our era of computing.

In any form of communication the information is sent by a "sender" and received by a "receiver." To secure the information it can be encrypted by a specific mathematic algorithm via a specified "key." As soon as the information arrives at the receiver, if s/he knows the required key then the process can be reversed. Let's introduce two terms: "plaintext" means un-encrypted data, while  "ciphertext" means encrypted data.

Almost all of the legacy (and simple) encryption algorithms work on a user-specified key. That means that technically anybody who knows the key is able to decrypt and regenerate the secured information into its original form — plaintext. If the "attacker" doesn't knows the exact key then the whole decryption process requires a lot of effort but mostly time and resources. More about this later on.

Real-World Encryption Algorithm Examples

In this section we will venture into the coding of encryption algorithms. All of these examples involve working with files. So you might want to create a test text document. It is up to you.