<p>The capability of encrypting top secret information remains as a major research problem in the GGH cryptosystem, which depends on various attacking methods. The early approaches to attacking the GGH cryptosystem mainly relied on special properties of the lattice generated by the vectors of the private key. Consequently, those attacks are not appropriate for general cases.</p> <p>This thesis presents a GGH attacking method for general cases. A lattice basis reduction algorithm is applied to the public key to get a better basis, which is used to decrypt the ciphertext. In the proposed approach, we concentrate on three lattice reduction algorithms: the LLL algorithm, the approximate optimally-reduced algorithm, and the optimally-reduced algorithm. We have implemented a package in MATLAB for the GGH cryptosystem and the three algorithms. We experimented with two groups of experiments and obtained promising results for lattices of low dimensions.</p> / Thesis / Master of Science (MSc)

The chasm in the protection of classified information in South African government indicates that all the departments have at their disposal information that is to some extent sensitive in nature and obviously requires security measures. This study shows that government officials who in their official duties come to contact with classified information are either vulnerable or are implementing the security controls incorrectly. It is also clear that in the absence of a comprehensive statutory framework, the government departments’ classified information has resulted in an unstable and inconsistent classification and declassification environment. The statutory framework would, in addition to other things, address the rising threat of espionage and antagonistic activities, the selling of information and the protection of critical records in government, without hindering the constitutional rights of citizens to access information. This would create a system of valuable informantion and clarify which information requires security measures with respect to the protection of classified information. / Kgaohanao e tshireletsong ya tlhahisoleseding e sireleditsweng ke mmuso wa Afrika Borwa e supa hore mafapha ohle a ona a na le tlhahisoleseding eo, ka ho hong, e leng ya sephiri mme e hloka maemo a tshireletso. Boithuto bona bo bontsha hore bahlanka ba mmuso bao, tshebetsong ya bona ya semmuso, ba teanang le tlhahisoleseding ya sephiri, ba kotsing hobane ba sebedisa ditaelo tsa polokeho ka mokgwa o fosahetseng. Ho boetse ho hlakile hore, bosikong ba moralo o phethahetseng wa semolao, disistimi tse sa sebetseng hantle tsa mafapa a mmuso tsa tlhahisoleseding ya sephiri di bakile tikoloho e sa tsitsang hape e sa hlophiswang ya tlhophiso le tloso ya tlhophiso ya tlhahisoleseding. Moralo wa semolao, hara tse ding, o ka sebetsana le phephetso e eketsehang ya bohlwela le diketsahalo tse ding tse belaetsang tse jwalo ka thekiso ya tlhahisoleseding, mme o sireletse direkote tsa mmuso tsa bohlokwa ntle le ho hatakela tokelo ya Molaotheo ya baahi ya phihlello ho tlhahisoleseding. Hona ho ka theha sistimi ya tlhahisoleseding ya bohlokwa le ho hlakisa hore na ke tlhahisoleseding efe e hlokang maemo a tshireletso ha ho tluwa ntlheng polokeho ya tlhahisoleseding ya sephiri. / Umsantsa okhoyo ekukhuseleni ulwazi olukhethekileyo kurhulumente woMzantsi Afrika ubonisa ukuba onke amaSebe anolwazi analo olunokuba nkenenkene, kwaye oludinga ukhuseleko. Esi sifundo sibonisa ukuba asesichengeni amagosa karhulumente aye athi apha ekusebenzeni kwawo, adibane nolwazi olukhethekileyo, ngoba azisebenzisa gwenxa iindlela zokulawula ukhuseleko. Kukwacaca ukuba, ekubeni kungekho sikhokelo namigaqo isemthethweni, iinkqubo ezingasebenzi kakuhle zamaSebe karhulumente, ulwazi olukhethekileyo aluhlelwa ngendlela eyiyo kwaye lufumaneka kwiimeko ezingaluphathi ngokukhetheka. Ubukho besikhokelo nemigaqo yokhuseleko lolwazi inganceda ekunqandeni isoyikiso esikhulu sobhukuqo mbuso nezinye iziganeko ezikrokrisayo, ezifana nokuthengiswa kolwazi, Esi sikhokelo singanceda nasekukhuseleni iingxelo zikarhulumente ezinkenenkene ngaphandle kokucinezela amalungelo abemi okufumana ulwazi njengoko uvuma uMgaqo Siseko. Oku kuya kuvelisa inkqubo yolwazi olunexabiso kwaye kuya kucacisa ukuba loluphi ulwazi oludinga imimiselo yokhuseleko malunga nokukhuselwa kolwazi olukhethekileyo. / Criminology and Security Science / M. Tech. (Forensic Investigation)