There are five types of operations in block cipher modes, ECB (Electronic Code Block) mode, CBC (Cipher Block Chaining) mode, CFB (Cipher Feedback) mode, OFB (Output Feedback) mode and CTR ( Counter) mode. J. Daemen, R. Govaerts, and J. Vandewalle, "Resynchronization weakness in synchronous stream ciphers," Advances in Cryptology - EUROCRYPT '93. E. Biham and P. C. Kocher, “A known plaintext attack on the PKZIP stream cipher,” Fast Software Encryption-Leuven ’94. Golic, "Recent advances in stream cipher cryptanalysis,". The keychain is a one-way chain such that Ki can be derived from Kj if i≤j, such as a keychain Ki (i=0,…,n), Ki=F(Ki+1), where F is a one-way function. Black and white pixels are treated as 0 and 1 bits, respectively. E. Biham and P. C. Kocher, "A known plaintext attack on the PKZIP stream cipher," Fast Software Encryption - Leuven '94. The longer keystream improved WPA’s protection against the well-known key recovery attacks on WEP, since finding two packets encrypted using the same key sequences is literally impossible due to the extremely long keystream. 6]. Tom St Denis, Simon Johnson, in Cryptography for Developers, 2007. S. Lucks, “Faster Luby-Racko. Cryptographic Boolean functions and their applications have been studied in the excellent and detailed books by Cusick and Stănică [96] (2009) and Logachev et al. Let c be an integrity checksum function. It is shown how to convert any keystream generator into a stream cipher with memory and their security is discussed. Stream ciphers can be broadly classified into those that work better in hardware and those that work better in software. μTESLA has specific requirements on the use of keys for producing MACs. The basic design of most ciphers was fairly consistent: find a somewhat nonlinear function and iterate it enough times over the plaintext to make the mapping from the ciphertext back to plaintext difficult without the key. Other than the issues we mentioned, there are no known attacks on RC4 itself as of this writing, and it seems to be an OK cipher (the attacks we talk about are actually targeted at poor implementations of RC4 in a system). Currently, this is believed to be the case for AES for all three supported key sizes. Specifically, the implementation artificially shortened the key period; the technical reason this is a problem will be explained shortly. This means that they process the plaintext in blocks of 64 or 128 bits. This is a common mistake in stream cipher implementation, and was one implementation error in WEP [20]. J. Daemen, R. Govaerts, and J. Vandewalle, “Resynchronization weakness in synchronous stream ciphers,” Advances in Cryptology-EUROCRYPT ’93. However, they serve a useful role in the defender’s resistance strategy. Enterprise deployment of WPA is required to be used with IEEE 802.1x authentication, which is responsible for distributing different keys to each user. This reduces the time needed for roaming clients to move from one access point to another, and it is especially useful for timing-sensitive applications. Implemented based on shared key secrets and the RC4 stream cipher [2], WEP’s encryption of a frame includes two operations (see Figure 10.4). With TKIP, WPA will dynamically change keys used by the system periodically. It is also possible for a block cipher to act as a stream cipher by setting a block size of 1 bit. It appears to be more difficult to adequately include stream ciphers in cryptosystems. Rather new and unusual designs can thus be obtained, such as the designs of block ciphers and (keyed) hash functions based on clock-controlled shift registers only. The algorithms are exactly the same though, and as a result, there is no effective difference between the two. For details on how a stream cipher can be successfully implemented, consult explanations of the Wi-Fi Protected Access (WPA) protocol, for example, in Stallings [22, ch. The shared key k is concatenated to the end of the initialization vector (IV) v, forming. is then used as the input to the RC4 algorithm to generate a keystream RC4(v,k). X. Lai and R. A. Rueppel, “A fast cryptographic checksum algorithm based on stream ciphers,” Advances in Cryptology-AUSCRYPT ’92. Encryption. Due to the XOR operation, once a stretch of key material has been used it can never be used again. It is shown how to convert any keystream generator into a stream cipher with memory and their security is discussed. B. Preneel, R. Govaerts, and J. Vandewalle, "Hash functions based on block ciphers: a synthetic approach," Advances in Cryptology - CRYPTO '93. Boolean functions that are used in cryptographic applications (e.g., in block or stream ciphers) should satisfy special conditions as far as it is necessary for guaranteeing the security of a cipher against different kinds of cryptanalysis. The user will respond with corresponding authentication information. As we shall see in Chapter 5, “Hash Functions,” hashes are equally versatile, and knowing when to tradeoff between the two is dependent on the problem at hand. The cryptographic properties of Boolean functions consist of the following: high degree, balancedness, correlation immunity and r-resilience, high nonlinearity, algebraic immunity, etc. Stream ciphers use conceptual tools similar to block ciphers. M. Bellare, J. Kilian, and P. Rogaway, "The security of cipher block chaining," Advances in Cryptology - CRYPTO '94, M. Bellare, A. Desai, E. Jokipii, and P. Rogaway, "A concrete security treatment of symmetric encryption: analysis of the DES modes of operation,", E. Biham and A. Shamir, "Differential cryptanalysis of DES-like cryptosystems,". Thus packets can be authenticated when the authentication keys have been disclosed. separate theme. Jason Andress, in The Basics of Information Security (Second Edition), 2014. The shared key k is concatenated to the end of the initialization vector (IV) v, forming . is then used as the input to the RC4 algorithm to generate a keystream RC4(v,k). A general stream cipher with memory in which each cipher-text symbol depends on both the current and previous plaintext symbols, as well as each plaintext symbol depends on both the current and previous ciphertext symbols, is pointed out. On one hand, the modes enable you to process arbitrary length data stream. Computational complexity and cryptography. M. Matsui, “Linear cryptanalysis method for DES cipher,” Advances in Cryptology-EUROCRYPT ’93, U. M. Maurer and J. L. Massey, “Cascade ciphers: the importance of being first,”. Chunming Rong, Erdal Cayirci, in Computer and Information Security Handbook, 2009. Likewise, combining two ciphertexts encrypted with the same key eliminates the key, since it is XOR’d with itself. TESLA does not use any asymmetry cryptography, which makes it lightweight in terms of computation and overhead of bandwidth.