Basic Concept Of Cryptography

What is Cryptography?

Cryptography is the art and science of making a cryptosystem that is capable of providing information security. Cryptography deals with the actual securing of digital data. It refers to the design of mechanisms based on mathematical algorithms that provide fundamental information security services. You can think of cryptography as the establishment of a large toolkit containing different techniques in security applications.

In computer science, cryptography refers to secure information and communication techniques derived from mathematical concepts and a set of rule-based calculations called algorithms to transform messages in ways that are hard to decipher. These deterministic algorithms are used for cryptographic key generation and digital signing and verification to protect data privacy, web browsing on the internet and confidential communications such as credit card transactions and email.

What is Cryptanalysis?

The art and science of breaking the cipher text is known as cryptanalysis. Cryptanalysis is the sister branch of cryptography and they both co-exist. The cryptographic process results in the cipher text for transmission or storage. It involves the study of cryptographic mechanism with the intention to break them. Cryptanalysis is also used during the design of the new cryptographic techniques to test their security strengths.

Primary Functions Of Cryptography

There are five primary functions of cryptography today:

1. Privacy/confidentiality: Ensuring that no one can read the message except the intended receiver.

2. Authentication: The process of proving one's identity.

3. Integrity: Assuring the receiver that the received message has not been altered in any way from the original.

4. Non-repudiation: A mechanism to prove that the sender really sent this message.

5. Key exchange: The method by which crypto keys are shared between sender and receiver.

Encryption and Decryption

Data that can be read and understood without any special measures is call plaintext or cleartext.the method of disguising plaintext in such a way as to hide it's substance is call encription.Encrypting plaintext result in unreadable gibberish called ciphertext.you use encryption to make sure the information is hidden from anyone of reverting ciphertext to its original plaintext is called decryption.

The following figure show this proccess.

The encryption and decryption is based upon the type of cryptography scheme being employed and some form of key. For those who like formulas, this process is sometimes written as:

where P = plaintext, C = ciphertext, E = the encryption method, D = the decryption method, and k = the key.

In this document, two communicating parties will be referred to as Alice and Bob; this is the common nomenclature in the crypto field and literature to make it easier to identify the communicating parties. If there is a third and fourth party to the communication, they will be referred to as Carol and Dave, respectively. A malicious party is referred to as Mallory, an eavesdropper as Eve, and a trusted third party as Trent.

Finally, cryptography is most closely associated with the development and creation of the mathematical algorithms used to encrypt and decrypt messages, whereas cryptanalysis is the science of analyzing and breaking encryption schemes. Cryptology is the term referring to the broad study of secret writing, and encompasses both cryptography and cryptanalysis.