Introduction

Encryption is a technique for transforming information on a computer and it is essentially to translate normal text into cipher text. Encryption can help ensure that data doesn’t get read by the wrong people, but can also ensure that data isn’t altered in transit, and verify the identity of the sender.

 

Three main types:

There are three basic encryption methods: hashing, symmetric cryptography, and asymmetric cryptography are as below.

o Hashing

Hashing creates a unique, fixed-length signature for a message or data set. Each “hash” is unique to a specific message, so minor changes to that message would be easy to track. Once data is encrypted using hashing, it cannot be reversed or deciphered.

o Symmetric methods

Symmetric encryption is also known as private-key cryptography, and is called so because the key used to encrypt and decrypt the message must remain secure, because anyone with access to it can decrypt the data. Using this method, a sender encrypts the data with one key, sends the data and then the receiver uses the key to decrypt the data.

o Asymmetric methods

Asymmetric encryption, or public-key cryptography, is different than the previous method because it uses two keys for encryption or decryption. With this method, a public key is freely available to everyone and is used to encrypt messages, and a different, private key is used by the recipient to decrypt messages.

 

Hashing – how it works:

The key in public-key encryption is based on a hash value. This is a value that is computed from a base input number using a hashing algorithm. Essentially, the hash value is a summary of the original value. The important thing about a hash value is that it is nearly impossible to derive the original input number without knowing the data used to create the hash value. Here’s a simple example:

Input Number	Hashing Algorithm	Hash Value
10,667	Input# x 143	1,525,381

 

You can see how hard it would be to determine that the value 1,525,381 came from the multiplication of 10,667 and 143. A 128-bit number has a possible 2128, or 3,402,823,669,209,384,634,633,746,074,300,000,000,000,000, 000,000,000,000,000, 000,000,000 different combinations — this would be like trying to find one particular grain of sand in the Sahara Desert.

Symmetric cryptography – how it works:

Let’s assume that Alice wants to talk to Bob. She wants to keep the message secret. Bob is the only one who should be able to read the message. The message is confidential, so Alice uses a key to encrypt the message. The original message is called a plaintext while the encrypted message is called a ciphertext. The ciphertext is sent to Bob, who knows the key and uses the same symmetric cipher (e.g., AES or 3DES). Thus Bob is able to decrypt the message.

Asymmetric cryptography:

Two keys are used in asymmetric cipher (e.g., RSA)—a public and a private one. The public one is available for everyone, but the private one is known only by the owner. When the message is encrypted with the public key, only the corresponding private key can decrypt it.

Asymmetric cipher solves the problem of secure key distribution. Alice takes Bob’s public key and uses it to encrypt the session key. Only Bob can then decrypt the encrypted session key, because he is the only one who knows the corresponding private key. Asymmetric ciphers are quite slow when compared with the symmetric ones, which is why asymmetric ciphers are used only to securely distribute the key. Then, Alice and Bob can use symmetric cipher and the session key to make the communication confidential.

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