Cryptography Reference
In-Depth Information
Rotation A computer operation where a word (consisting, for example, of 32 bits) is
shifted to the left or right by a few bits, and the bits pushed out are shoved back in
again at the other side. In this topic, rotation is mainly relevant for RC5. Example:
right-rotating the binary number 00001011 by 2 bits produces 11000010.
Rotor A rotating disk with 26 (or more) sliding contacts each on its outer sides, which
are internally wired such that each contact on the left side connects exactly with a
contact on the right side. This means that rotors implement a substitution in hard-
ware that depends on the rotor's position. Rotors were used in rotor machines ,
with the Enigma being the best-known representative (see Section 2.5.1).
Round, round's key See 'product algorithm'.
S-boxes Special substitution tables used in the DES algorithm; they are the most
important component for the security of this algorithm.
Serpent The proposal submitted by Anderson, Biham, and Knudsen to the AES chal-
lenge. It is presumably the most secure algorithm among the five final candidates,
but not the fastest.
SESAME The European project initially conceived as the Kerberos substitute. The
software had serious cryptological weaknesses (see Section 6.7).
Session key A random key created by a computer for use in a symmetric method. It
is valid only for the duration of the transmission of a single message and often
distributed by means of asymmetric encryption (see 'hybrid method').
SETUP system (Secretly Embedded Trapdoor with Universal Protection) A term intro-
duced by Young and Yung to refer to Trojan cryptography, where parts of the
private key are hidden in the public key in software or hardware such that the
fraud cannot be proved by analyzing the output (see Section 6.7).
SHA See 'DSA'.
Skipjack algorithm A secret encryption algorithm developed by the NSA for the
Clipper and Capstone chips (see Section 5.7.5).
Snefru Probably the first one-way hash function (see Section 6.3.1).
Stream cipher In contrast to block algorithms, a continuous (symmetric) encryption,
where a byte or bit stream is created in dependence on a secret key, and that
stream is XORed with the plaintext or ciphertext. The bit stream is also called
key stream and used like a one-time pad (see Section 4.1.3).
Substitution A way of encrypting by systematically substituting the plaintext characters
based on a given permanent table. The substitution encryption is very vulnerable
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