The Vernam cipher is the name of various encryption methods that go back to Gilbert Vernam . Originally, a method was patented by Vernam in 1918 in which a key stream bit by bit to a message added is.
The security of the process depends crucially on how the keystream is generated.
- If only a long natural-language password is chosen as the key , the Vernam cipher is an extension of the Vigenère cipher , in which the secret key has the same length as the plain text . Such a procedure is unsafe by today's standards.
- If the key is generated by a cryptographically secure random number generator, the resulting method is stream encryption , the security of which depends on that of the random number generator.
- If the key is genuinely randomly generated, the process is also called a one-time pad . Since the one-time pad was co-developed by Vernam, it is also often referred to as the Vernam cipher. In terms of information theory, this procedure is secure .
- Patent US1310719 : SECRET SIGNALING SYSTEM. Filed September 13, 1918 , published July 22, 1919 , applicant: AT&T , inventor: Gilbert S. Vernam (PDF at Google Patents ).
- Klaus Schmeh: Cryptography. 3. Edition. dpunkt.Verlag, Heidelberg 2007, ISBN 978-3-89864-435-8 , p. 49