Ajay Ohri

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What is a cipher? Cipher is a method in which a message is transformed to conceal its real meaning. The term finds use in cryptograms and the ciphertext.

**Definition of Cipher****How does cipher work?****Uses of Cipher in Cyber Security****Types of Cipher in Cryptography**

Here is how we define cipher. Cipher is an algorithm that is used widely in cryptology which is a discipline that concerns the study of the cryptographic algorithm. Cipher is used to encrypt and decrypt data. The secret or the symmetric key encryption will depend on the cipher’s use that operates symmetrically. With the use of the symmetric algorithm, the same encryption key and cipher gets applied to the data in the same way. The objective could either be to convert the plain text to ciphertext or vice versa. The cipher processes the original and plaintext data to transform it into a ciphertext that appears to look like some random data.

Earlier the cipher made use of two kinds of transformations. These were the transposition ciphers that keep the original data bits in a byte but mix their order. The other is the substitution cipher that replaces the specific sequence of data with another particular data sequence. The data output that is got from either of the two methods is the ciphertext.

The modern methods of cipher use private communication in various networking protocols like the TLS or the transport layer security that allows for the encryption of the network traffic. There are many kinds of communication technologies like digital televisions, phones, and ATMs that make use of a cipher to ensure privacy and security. This should solve your question on what is a cipher.

The working of a cipher is pretty interesting. It uses a fixed set of rules or algorithms to transform the plaintext or a legible message into a ciphertext that is nothing but a string of random characters. The ciphers could be designed to encrypt or to decrypt the bits into stream ciphers. Or they may process the ciphertext into uniform blocks of a particular number of bits which is called block ciphers.

The modem method of cipher implementation relies on the algorithm of the cipher and the secret key that is used by the algorithm to modify the data as the data is encrypted. Also, the ciphers that make use of long keys that get measured in bits are more secure from any kind of brute force attack. This is because when the length of the key is longer there is a need for more brute force attempts for the plaintext to get exposed. The strength of the cipher may not always be dependent on the key length however still the modern ciphers are configured to use keys that are either 128 bits, 1024 bits, or more.

A major part of the cipher algorithm is the key. In the real world of ciphering, the key is hidden and not the algorithm. The strong ciphers are designed such that if even one traces the algorithm it is impossible to understand the ciphertext without knowing what the appropriate key is. Also before the cipher can work the sender as well as a receiver should have a set of keys.

The symmetric ciphers are used in any kind of secure online communications that get incorporated into various kinds of network protocols that are used in encrypting the exchanges. Like for example, the Secure Sockets Layer or SSL and the TLS make use of the ciphers to encrypt the layers of application data especially when it is used with the HTTPS.

The virtual private networks or the VPNs are what connect the remote workers or the remote branches into the corporate networks. This does use protocols and the symmetric ciphers that are used to protect the data communication. The symmetric ciphers protect the privacy of data in most of the Wi-Fi networks, e-commerce sites, and banking services.

Some of the protocols like the OpenPGP and the Secure Sheet or the SSH make use of asymmetric cryptography to authenticate and encrypt the endpoints. It also allows the secure exchange of the symmetric keys to encrypt the data session. Public key cryptography is more secure than symmetric encryption but computationally it is more extensive. This is why for performance reasons the protocols rely most on ciphers to encrypt the session data.

The modern-day ciphers can withstand the attacks even when the cipher is aware of what the cipher is used for. Historically the ciphers were less secure against these attacks because these were ciphered with the hand and thus could be easily broken down using the power of computers.

Here are some of the types of ciphers:

- Caesar cipher is a simple cipher substitution where every element gets shifted to a specific count of places down in the alphabet.
- Atbash cipher is a kind of substitution cipher where the plaintext alphabet gets mapped onto itself however in the reverse order
- A simple substitution cipher is where every plaintext character was substituted for a different character that made a 26 character key.
- Vigenère cipher is a type of polyalphabetic substitution where it makes use of multiple alphabets for substitution.
- A homophonic substitution cipher is a cipher substitution where many of the ciphertext letters will replace the single plaintext letter.

These were some of the cipher examples.

The ciphers get characterized into block ciphers that encrypt the blocks of data that are sized uniformly and the stream ciphers that are applied to a data stream that is sent and received over a network. The cryptographic ciphers are used to covert the ciphertext to plaintext and back.

In symmetric cryptography, the same key is used to encrypt and to decrypt data while in the case of asymmetric cryptography or public-key cryptography, private and public keys are used to encrypt and decrypt data.

Cipher is thus a way to encrypt a message. It converts a message using the cipher algorithm to transform the data that represents the words and letters in the message. Ciphers can be implemented fast and the algorithm that is used in cipher is automated and programmed easily.

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