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# what is the idea of stream ciphers

what is the idea of stream ciphers

stream cipher is a symmetric key cipher where plaintext digits are combined with a pseudorandom cipher digit stream.

In-stream cipher Encryption and Decryption are done on one symbol (such as a character or a bit) at a time.

## How does a stream cipher work?

A stream cipher is an encryption algorithm that uses a symmetric key to encrypt and decrypt a given amount of data. An asymmetric cipher key, as opposed to an asymmetric cipher key, is an encryption tool that is used in both encryption and decryption.

### For Encryption,

Plain Text and Keystream produce Cipher Text (The same keystream will be used for decryption.).

The Plaintext will undergo XOR operation with keystream bit-by-bit and produces the Cipher Text.

Plain Text: 10011001

Keystream: 11000011

`````````````````````

Cipher Text: 01011010

For Decryption,

Cipher Text and Keystream give the original Plain Text (The same keystream will be used for encryption.).

The ciphertext will undergo XOR operation with keystream bit-by-bit and produces the actual Plain Text.

Cipher Text: 01011010

Keystream: 11000011

``````````````````````

Plain Text: 10011001

## ----------------------- Types of Stream Cipher --------------------

### Synchronous stream ciphers

This state is updated in essentially two ways: if the state changes independently of the plaintext or ciphertext messages.

In an asynchronous stream cipher, a stream of pseudorandom digits is generated independently of the plaintext and ciphertext messages and then combined with the plaintext (to encrypt) or the ciphertext (to decrypt).

binary additive a stream cipher is the term used for a stream cipher which XOR's the bits with the bits of the plaintext. Encryption and decryption require that the synchronous state cipher is in the same state, otherwise, the message cannot be decrypted.

### Self-synchronizing stream ciphers

Such schemes are known as self-synchronizing stream ciphersasynchronous stream ciphers, or ciphertext autokey (CTAK). The idea of self-synchronization was patented in 1946 and has the advantage that the receiver will automatically synchronize with the keystream generator after receiving N ciphertext digits.

## Stream cipher vs. block cipher

Block ciphers and stream ciphers, while similar, are two distinct forms of symmetric key encryption. The main difference between these two modes of operations is the amount of data they encrypt at one time.

While stream ciphers perform data encryption one bit at a time, block ciphers encrypt fixed blocks of information all at once. These predetermined blocks of data will typically be either 64 or 128 bits long.

## Stream Cipher Vulnerabilities

Key Reuse

Bit-flipping Attack