Symmetric encryption

M. Bellare, A. Desai, E. Jokipii and P. Rogaway, A Concrete Security Treatment of Symmetric Encryption Analysis of the DES Modes of Operation, Proc. of 38th IEEE Symposium on Foundations of Computer Science, 1997, pp. 394 03. 

E. Fujisaki and T. Okamoto, Secure Integration of Asymmetric and Symmetric Encryption Schemes, Advances in Cryptology - CRYPTO 1999, Lecture Notes in Computer Science, Vol. 1666, 1999, pp. 537-554. 

Cryptography can be divided into two groups symmetric and asyrrrmetric encryption. In symmetric encryption the sender and receiver use the same key. This method is very fast but the sender needs to send not only the message but also the key, otherwise the receiving party carmot read the message. 

For symmetric encryption the sender sets the algorithm mode setAlgorithm-Mode), performs a key-exchange protocol if a shared key is not already exchanged, and requires the exchange of certificates. We have modelled the ISO/IEC 11770-3... 

Supports Encryption. The authorisation ticket issued by the TTP holds a symmetric encryption key. This key is not hmited to provide mutual authentication and to ensure the integrity of messages, but can also be used to encrypt the whole session between diagnostics equipment and vehicles. 

In practice, however, to this day, schemes with even greater efficiency are used for symmetric authentication, instead of information-theoretically secure ones schemes about whose security no precise knowledge exists. Most common are certain modes of operation of the (former) Data Encryption Standard (DES). (See, e.g., [DES77] for the standard, [DaPr89] for modes of operation and possible applications, and [BiSh93] for new security examinations.)... 

Symmetric key cryptosystem A traditional single-key cryptosystem, in which the same key is used for encryption and decryption. 

Often, Ke = that is, the encryption and decryption keys are identical, and in this case we refer to it simply as the key or the secret key. This is called symmetric or secret key cryptography. In contrast, in asymmetric or public key cryptography, the encryption keys and decryption keys are different from each other, and only the decryption key needs to be kept secret. In public key cryptography, the decryption key is also sometimes called the secret key. 

Traditionally, all cryptography was symmetric key cryptography. In a symmetric key cryptosystem, the encryption key Ke and the decryption key Kd are the same, denoted simply by K. The key K must be kept secret, and it is also important that an eavesdropper who sees repeated encryptions using the same key can not learn the key. The simple substitution cipher described earlier is an example of a symmetric key cryptosystem. 

A new Sg S-box is obtained by using the action of symmetric group Sg on AES S-box [17], and these new S-boxes are used to construct 40320" ° secret keys [13]. The creation of the encryption keys with the permutations of the existing S-boxes results in 40320 new S-boxes, which, in turn, enhances the security and allows the system to be more safe and reliable. As a result, the information can be transmitted more securely over an unsecure and open access channel. 

Finally, the defensive measures that are proposed to deal with the presented attacks and that are suitable for the unique characteristics of a WSN (either in the form of a WBAN or a WPAN) include key estabhshment and encryption. Especially, symmetric cryptography with the use of shared keys is preferred over techniques that include use of both private and public keys, because of the greater energy consumption needed by the latter. 

Symmetric key cryptography uses a polyalpha-betic encryption algorithm, such as a block cipher, a stream cipher, or a hash function to convert the data into binary code. A block cipher apphes the same key to each block of data. Stream ciphers encrypt the data bit by bit. They can operate in several ways, but two common methods are self-synchronizing and synchronous. The self-synchronizing cipher encrypts the data bit by bit, using an algebraic function applied to the previous bit. Synchronous ciphers apply a succession of functions independent of the data. 

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