Konstruksi Kelas Kunci Lemah pada Kriptosistem IDEA Berdasarkan Faktor Linear dan Kriptanalisis Diferensial

Abstract

Cryptography is the study of mathematical techniques related to aspects of information security such as confidentiality, data integrity, entity authentication and data origin authentication. In cryptography, a common way to secure information or document is to disguise the message you want to send a different message, then the message will be seen by those who have the authority to make the process of reversal of messages that have been disguised. The information disguises process known as cryptosystems. Cryptosystem divided into two parts : symmetric and asymmetric cryptosystems. In this thesis we study cryptanalysis of IDEA (International Data Encryption Algorithm). IDEA algorithm is an algorithm that operates with a block size of 64 bits by using the same key size of 128 bits. This algorithm uses mixed operations are multiplication modulo operation (216 + 1), addition modulo operation (216) and bitwise XOR. In this study is conducted a theoretical study relating to the construction of a weak key classes on IDEA cryptosystems and affirmation of the tables that have been created by Daemen. The construction of a weak key classes is based on linear factor and differential cryptanalysis. There are three objectives of this study, namely: (1) to assess proposition associated with the construction of a weak key classes on IDEA cryptosystems, (2) to construct a weak key classes based on factor linear and differential cryptanalysis, (3) to recover weak keys in IDEA cryptosystems. The construction of the weak key classes based on linear factor resulting global linear equations that are used to lower the chances of recovery of the bits that are not known yet. While the construction of the weak key classes based on differential cryptanalysis where at the seventh round was not required to produce a weak key class 266