A stream cipher is a symmetric cryptosystem (see key) which operates with a time-varying transformation on individual plaintext digits. By contrast, block ciphers operate with a fixed transformation on large blocks of plaintext digits. More precisely, in a stream cipher a sequence of plaintext digits, \(m_0 m_1 \ldots\), is encrypted into a sequence of ciphertext digits \(c_0 c_1 \ldots\) as follows: a pseudorandom sequence \(s_0 s_1 \ldots\), called the running-key or the keystream, is produced by a finite state automaton whose initial state is determined by a secret key. The ith keystream digit only depends on the secret key and on the \((i-1)\) previous plaintext digits. Then, the ith ciphertext digit is obtained by combining the ith plaintext digit with the ith keystream digit.
Stream ciphers are classified into two types: synchronous stream ciphers and asynchronous stream ciphers. The most famous stream cipher is the Vernam cipher, also called one-time pad, that leads to perfect...
This is a preview of subscription content, log in via an institution to check access.
References
Rueppel, R.A. (1986). Analysis and Design of Stream Ciphers. Springer-Verlag, Berlin.
Vernam, G.S. (1926). “Cipher printing telegraph systems for secret wire and radio telegraphic communications.” Journal of the American Institute of Electrical Engineers, 55, 109–115.
Editor information
Editors and Affiliations
Rights and permissions
Copyright information
© 2005 International Federation for Information Processing
About this entry
Cite this entry
Canteaut, A. (2005). Stream Cipher. In: van Tilborg, H.C.A. (eds) Encyclopedia of Cryptography and Security. Springer, Boston, MA . https://doi.org/10.1007/0-387-23483-7_412
Download citation
DOI: https://doi.org/10.1007/0-387-23483-7_412
Publisher Name: Springer, Boston, MA
Print ISBN: 978-0-387-23473-1
Online ISBN: 978-0-387-23483-0
eBook Packages: Computer ScienceReference Module Computer Science and Engineering