A stream cipher is a method of encrypting text where a cryptographic key and an algorithm are applied to each binary digit in a data stream, one bit at a time.
The stream cipher is also known as state cipher.
Encryption is 1 bit or byte of plaintext at a time.
Stream cipher uses an infinite stream of pseudorandom bits as the key.
To remain secure, a stream cipher pseudorandom generator should be unpredictable and the key should never be reused.
The pseudorandom cipher digits are generated through a number of random seed values that use digital shift registers.
The encryption of each digit is dependent on the current state of the cipher, thus the name state cipher.
- Read: What is the ciphertext.
This cipher is designed to work in the same way as the one-time pad.
What is the difference between a stream cipher and block cipher
While the stream cipher encrypts 1 bit of the plaintext at a time, block cipher encrypts blocks of data at a time.
Stream ciphers are preferred in cases where speed and simplicity are both required.
- Read: What is a block cipher.
One advantage of stream ciphers over block ciphers is that they are operating on the smallest possible unit thus eliminating the need for padding.
Popular Stream Ciphers
Rivest Cipher 4 (RC4 or ARCFOUR or ARC4) – it is used in security protocols for wireless networks like WEP, WPA, and TLS. It’s not secure today as vulnerabilities have been discovered.
Stream cipher list
- ChaCha (a variant of Salsa20)
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