In the last few decades the science and study of cryptography has earned an outstanding reputation due to its insane applicability and efficiency. Cryptography is the science of message secrecy. Its importance is easily explicable -- it is used everywhere: online purchasing, secured money transfers, cellular phones, broadcast of TV channels, emails, confidential data, and so forth. Our life would be quite different without cryptography.
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.
Keep in mind that the encryption algorithms described in this article are solely for educational purposes. You should not rely on them for top-priority files and/or data. However, the author guarantees that the algorithms presented in this article willnot do any harm to your computer. They do not contain any virus, trojan, worm, spyware, malware, or anything that's malicious.