Block ciphers and stream ciphers
require random seed for encryption.
Holden goes on to explore polyalphabetic substitution ciphers, transposition ciphers, including one developed by the Spartans, connections between ciphers and computer encryption, stream ciphers
, and ciphers involving exponentiation.
This method uses a block cipher, which encrypts data one fixed-size block at a time, unlike other types of encryption, such as stream ciphers
, which encrypt data bit by bit.
The authors in  review different constructions for authenticated encryption using stream ciphers
as underlying primitives.
1- Symmetric (Secret-key) cryptosystems  where only one key is used for both encryption and decryption operations, and it is of two types: Block ciphers and stream ciphers
. Data Encryption Standard (DES), Advanced Encryption Standard (AES) and Blowfish are some examples of symmetric cryptography .
are known to be very area efficient when it comes to hardware implementation, but their sequential nature gives rise to the probability of the design consuming a lot of power.
are robust to adequate JPEG compression noise.
also are extensively studied in the cryptographic environment due to its quicker execution; however, they're vulnerable to attacks as compared to SP network block ciphers.
The existing stream ciphers
are vulnerable to frequency analysis attack, brute force attack, correlation attack, algebraic attack known plain text attack, cipher text only attack, etc.
Consequently, in this paper we consider the problem of designing a dedicated encryption/decryption algorithm which fits into the communications scenarios which include the following: (i) a high performance computing party should deliver encrypted messagesin a one-way communication scenario to a number of parties which have tiny computational capabilities; (ii) implementation limitations at the tiny entity imply employment of a lightweight keystream generator (from certain reported lightweight stream ciphers
); (iii) developed encryption scheme should have enhanced security in comparison with the one offered by the employed keystream generator.
can be classified as synchronous and asynchronous.
Moreover ciphers can be distinguished into two types by the type of input data; they are block ciphers, which encrypt block of data of fixed size, and stream ciphers
, which encrypt continuous streams of data.