Cryptography is the process of converting recognizable data into an unreadable code and then decrypting it and sent across a network (either trusted or untrusted). Data is encrypted at the source, i.e. sender’s end and decrypted at the destination, i.e. receiver’s end.

In all cases, the initial unencrypted data is referred to as plain text as shown below. It is encrypted into cipher text, which will in turn be decrypted into usable plaintext using different encryption algorithms.

Cryptography is used protect confidential data such as email messages, chat sessions, personnel data, e-commerce applications,Phone cards, cell phones, remote controls, Cash machines, money transfer between banks, Electronic cash, online banking, Satellite TV, etc.

Purpose of cryptography:

Authentication: The process of establishing the identity of a remote user (or system),A web server providing proof to the user that he or she is connected to the correct server.

Confidentiality: Ensuring that no one cans read the message except the intended receiver. Integrity: Assuring the receiver that the received message has not been altered in any way from the original.

Non-repudiation: A mechanism to prove that the sender really sent his message and assurance that receiver really received that message without any deny, andthe receiver can prove that the message he or she received is precisely what the sender sent.

Types of cryptography

1.Symmetric encryption: Data is encrypted and decrypted using the same key. Examples of symmetric algorithms are DES, 3DES and AES.
DES uses 56-bit keys, they are short enough to be easily brute-forced by modern hardware and it is recommended that DES should not to be used.
Triple DES (or 3DES) uses 128 bits key length, the same algorithm, applied three times to produce strong encryption.

2.Asymmetric encryption: Asymmetric encryption use two keys, one to encrypt the data, and another key to decrypt the data. These keys are generated together. One is named as Public key and is distributed freely. The other is named as Private Key and it is kept hidden.
Example: RSA

3.Hashes: Hash functions takes arbitrary input, it might be a key or password andproduces a fixed-length string based on this input. Hash functions used in cryptography have the property that it is easy to calculate the hash, but difficult or impossible to re-generate the original input if only the hash value is known. It’s not possible to go from the output to the input. Examples are SHA-3,MD-5. Guys enough of the theory stuff right ??!! Now we will see how it really works…!!
I have used one of cryptographic tool for encryption and decryption.

Step 1: This is ‘The Cryptographic tool 1.1 RC’, here click on Add files to select file for encrypting.

Step 2: Click on Add files, and select file from desired folder.

(This is the file which I have selected)

Step 3: Select ‘just encrypt with password’, give password, then click on encrypt.

Step 5: In this step, Encryption will be finished.

(Now you can see Encrypted file)

Step 6: Select on Decrypt, and specify the password. Then click on Decrypt button.

Step 7:After decryption we got the original file.