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# PPT on Secret Key Cryptography | 18 Slides

A power point presentation on the topic “Secret Key Cryptography” with a total of 18 slides.

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## Secret Key Cryptography

Contents

### Introduction

Secret key cryptography is effective for communication over insecure channels as the piece of information or parameter used helps the information to encrypt and decrypt messages.

There are two different keys used for asymmetric encryption in which one is a public key, the other is a secret key.

A secret key may also be known as a private key.

### What is Secret Key Cryptography ?

The secret key cryptography is used to encrypt the plaintext message using a series of bits called the secret key.

It often uses the same key to decipher the corresponding ciphertext message and to retrieve the initial plain text because both encrypting and decrypting data is achieved with the same key, a secret key is often called as a symmetric key.

The secret key in cryptography is also an input for encryption algorithm as this is the initial intelligible message or data that is fed into the algorithm as input. The main is an algorithm value independent from the plaintext.

Depending on the particular key used the algorithm outputs a different result. The algorithm relies on the key to exact substitution and transformation. This is the scrambled message that has been generated as production. It depends on the plain text and on the secret key.

Two different keys can generate two different ciphertexts for a given letter. The ciphertext is an almost random stream of data which as it stands. Decryption algorithm is basically a reverse-run encryption algorithm. It takes the ciphertext and the secret key, and it generates the original plain text.

In this type of cryptography, both the sender and the receiver must know the key, that it is in effect, the password. The main distribution, of course, is the greatest challenge with this method.

### Example of Secret Key Cryptography

A very basic method for encrypting messages is to replace each letter of the message with one that is several more places in the alphabet. The secret is the number of places.

For eg, the message “This is an example” can be encrypted using the key “1 position” in the encrypted message “Uijt jt bo fybnqmf” Taking a letter that is 1 position above in the alphabet would end in the original message again.

This device is not very stable. Just twenty-six keys are possible. One should only try all the keys and see which one can result in a readable message.

In addition, it is well known that certain letters appear more often in communications than others. For example, the letter “e” is the most used letter in the English language.

Using this reality, simply count the letter appears most frequently in the encrypted message and substitute it with the letter “e”. Then we knows how many places we needs to rotate to get from “e” to the encrypted version of “e”.

### Uses of Secret Key Cryptography

With secret key encryption, both Alice and Bob communicators use the same key to encrypt and decode texts. Before any encrypted data may be transmitted across the network, both Alice and Bob must have the key and agree on the cryptographic protocol to be used for encryption and decryption.

One of the big issues with secret key cryptography is the logistical dilemma of how to get the key from one party to the other without giving access to the attacker.

If Alice and Bob protect their data with secret-key cryptography, and if Charlie has access to their key, Charlie will understand any secret messages that Alice and Bob intercept.

Not only can Charlie decode the messages of Alice and Bob, but he can also believe that he is Alice and send encrypted data to Bob. Bob is not going to realize that the letter came from Charlie, not Alice.

When the issue of secret key dissemination is overcome, secret key cryptography may be a powerful method. Algorithms provide excellent protection and encrypt data reasonably easily.

The bulk of confidential data transmitted during an SSL session is sent using secret-key cryptography. Secret key cryptography is often called symmetric cryptography since the same key is used to encrypt and decrypt data.

Well-known hidden key cryptographic algorithms include Data Encryption Standard (DES), triple-strong DES (3DES), Rivest Cipher 2 (RC2), and Rivest Cipher 4 (RC4).

### Secret Key Algorithms

The AES Encryption algorithm (also known as the Rijndael algorithm) is a symmetric block cipher algorithm with a block/chunk size of 128 bits.

It converts these individual blocks using keys of 128, 192, and 256 bits. Once it encrypts these blocks, it joins them together to form the ciphertext

### Triple Data Encryption Standard (3DES)

3DES Encryption, also known as Triple Data Encryption Standard (DES), is a type of cryptography where block cipher algorithms are applied three times to each data block.

The key size is increased in Triple-DES to ensure additional security through encryption capabilities. Each block contains 64 bits of data

### Rivest Cipher 4 (RC4)

RC4 stands for Rivest Cipher 4. RC4 is a stream cipher and was invented by Ron Rivest in 1987. Since RC4 is a stream cipher, it encrypts the stream of data byte by byte.

Of all the stream ciphers, RC4 is the widely used stream cipher due to its speed of operations and simplicity.

### Advantages of Secret Key Cryptography

• High rates of data throughput, with hardware solutions up to hundreds of megabytes per second .
• Key length is relatively short.
• Symmetric – Key ciphers can also be combined to produce stronger ciphers.

### Disadvantages of Secret Key Cryptography

• The Key must remain secret at both ends.
• Cryptographic practice leads to frequent key change.
• In large networks, many key pairs have to be managed.