Security of information systems: Implementation of encryption

Thèmes abordés

Symmetric encryption, asymmetric encryption, digital signature, SSL.

Résumé du document

The security of computer systems is generally limited to guaranteeing rights of access to data and system resources by implementing authentication mechanisms and monitoring to ensure that users of these resources have only those rights that they were granted. The security mechanisms in place can still cause discomfort to users and guidelines and rules are becoming increasingly complicated as the network expands. Thus, IT (Information Technology) security must be studied in such a way that does not prevent users from developing uses that are necessary, and ensure that they can use the information system with confidence.

The concept of cryptography was born the moment man conceived ways of safeguarding his privacy and protecting certain facts/deeds from spies. From Julius Caesar and his army to Romeo and Juliet, encryption has been used over the ages in some form or the other. With the advent of net banking, technologically advanced military applications etc, the consumer world is riddled by many encryption requirements. Secrecy of communications on computer networks must be ensured and modern-day pirates must be prevented from infiltrating these networks of computers. Cryptography is used increasingly in various fields.

Until recently, the security of these systems was based on secret information shared by users, and enabled confidential communication. For this reason, this system is called secret key cryptography. Secret key systems use algorithms utilizing the same key for encryption and decryption;this algorithms are called symmetric encryption algorithms. DES, AES, IDEA are the most more popular examples of these algorithms. Although these algorithms are still used for encrypting messages owing to very high speeds, they no longer satisfy the new consumer needs. Public key cryptography has been formalized and helps meet these needs. These offer solutions to new problems including identification, authentication and confidentiality of messages.

Public key cryptography is involved in many everyday applications, the use of smart cards through mobile phones, or when a user logs in to a computer. However, the security of these applications depends mainly on two issues: number theory - the problem of factoring and the discrete logarithm problem. Although these two problems still hassle the cryptographers, the possibilities of a theoretical breakthrough or even quantum computers that would reduce the difficulty of solving them loom on the horizon.

Extraits

[...] Until recently, the security of these systems was based on secret informat ion that is shared by users, and allowed to communicate confidentially. For this reason, all of these systems is called secret key cryptography. As secret key systems, it uses algorithms using the same key for encryption and decryption and for this, are called symmetric encryption algorith ms. DES, A ES, IDEA are the most famous examp les. Although these algorithms are still used for encrypting messages because of very high speed, they no longer meet the new needs. [...]

[...] C The problem of key exchange For centuries the problem of key exchange was seen as a natural disadvantage of encryption. With the use of computer and tele-transmission, and the dematerialization of informat ion they allow the problem is different. In 1970 an independent researcher, Whitfield Diffie, reflected by two of ARPA NET users to exchange encrypted emails without physically meet beforehand to agree on the encryption key that they use it[2]. In 1974 he gave a lecture on the research center Thomas J. [...]

[...] A lin ear transformation is then applied to the matrix, it consists of a binary mu ltip licat ion of each element of the matrix with polynomials fro m an au xiliary mat rix, this increase is subject to special rules as GF (28 ) (Galo is group fin ite) [9,10]. The linear transformation ensures a better distribution (propagation of bits in the structure) on several laps. Finally, an XOR between the matrix and another matrix provides an intermediate matrix. These different operations are repeated several times and set a "tower". For a key of or 256, A ES requires respectively or 14 towers. [...]

[...] The operation is repeated sixteen t imes. The transformation function has variations depending on the key, which is an arbitrary nu mber chosen by the user code. The number of possible values for the key determines the n umber of ways in wh ich a message can be encrypted. The sender of the message secret number according to the DES algorith m using the key, the receiver applies the inverse function with the same key to decrypt it. In 1976 the standardization of DES has a limit on the key size to 56 bits.Today value is notoriously weak, and it uses the triple DES with a key length of 112 b its. [...]

[...] Of these 15 algorith ms, five were selected for further evaluation in April 1999: MA RS, RC6, Rijndael, Serpent, and Twofish. After this assessment, it was finally the candidate Rijndael, named after its two designers Joan Daemen and Vincent Rijmen (both Belgian nationality) who has been chosen [9,10]. These two experts in cryptography were already authors of another algorithm: Square. AES is a subset of Rijndael: it only works with blocks of 128 b its, whereas Rijndael offers block sizes and keys that are mult iples of 32 (between 128 and 256 bits). [...]