###### What is Cryptography?

Cryptography is a technique used to secure information and communications through the use of codes, so that only people who have access can understand and process them.

This information and communication techniques are  comes from mathematical concepts and rule-based calculations known as algorithms. This algorithm is used to change a message by making it difficult to decode.

The use of this algorithm includes the generation of cryptographic keys, digital signing, verification to protect data privacy, web browsing on the internet, credit card transactions and email.

Cryptography Components

There are several components in cryptography that need to be understood to explore the science of cryptography, including:

1. Plaintext : can be in the text, binary code, or images that have meaning that will be processed using an algorithm into ciphertext.
2. Ciphertext : an unreadable random message generated from plaintext encryption.
3. Encryption : receives information and converts it into an unreadable format (converts plaintext to ciphertext). Encryption uses a cipher and secret key algorithm.
4. Decryption : return ciphertext (encoded message) to plaintext (original message). Decryption uses a decryption and secret key algorithm. In symmetric encryption, the key used to decrypt is the same as the key used to encrypt. Whereas in asymmetric encryption or public-key encryption, the key used to decrypt is different from the key used to encrypt.
5. Cipher : rules or mathematical functions used to perform encryption and decryption.
6. Key : separate information ( a number or a series of numbers) used to control the output (ciphertext and plaintext) of a given cryptographic algorithm.

Cryptography Security Aspects

• Confidentiality : Protected information will not be accessible to all parties who are not entitled to the information.
• Integrity : The data to be received and sent can’t be changed without the knowledge of both parties.
• Non-repudiation : The sender or recipient will not be able to deny that they have sent or received a message.
• Authentication : The recipient and sender can find out the identity of each and source of the data they are using.

Types of Cryptography Methods

In general, the types of cryptography methods are divided into three:

1. Symmetric Key Cryptography : The receiver and sender of information only use one key to encrypt and decrypt the message. The type of cryptography that is often used in this method is AES (Advanced Encryption Systems).
2. Public Key Cryptography (Asymmetric Key Cryptography) : Allows the use of two keys, which are different for the sender and receiver. Both the sending and receiving parties have private and public keys. The private key must be kept secret while the public key can be known by any party who wants to communicate with the other. Public key cryptography is considered more secure and secure when compared to symmetric key cryptography. The cryptographic method that is often used in this method is RSA (Rivest Shamir Adleman).
3. Hash Function : This method depend on a mathematical equation, that is the algorithm will take a numeric value as input and generate a message that will be summarized by a hash. This method doesn’t involve a key, but uses a set-length hash value that is presented as plain text. Hash functions are used to check the integrity of the transferred data. There are various rounds of hashing operations, and each round considers the input to be an array of the most recent block thus producing the activity of the last round as output.