Research On Key Technologies Of Secure Storage Against Physical Attacks

Nowadays,information security has drawn extensive attention because of numer-ous issues on information leakage.As the carrier of information,the security of mem-ories is very important.However,the solid-state memories,represented by Flash mem-ory,are faced with various physical attacks.Meanwhile,the data remanence is also a threat.To protect the information security,this dissertation studies the key technologies of secure storage against physical attacks.Aiming at the threats of physical attacks,this dissertation proposes two generation algorithms of active shield and designs two differ-ent kinds of integrity detectors.In order to reduce the influence of the data remanence in Flash memories,two different erasure strategies,separately based on random time and overwriting sequence,are studied.The key circuits are also designed to realize the safe and efficient erasure.Finally,a secure memory is designed.The main work is as follows:The classical generation algorithm of random Hamiltonian path has low efficiency.Therefore,two highly-efficient algorithms are studied.Combining with the dynamic programming algorithm and the divide-and-conquer algorithm,a mixed optimization algorithm is proposed.Its efficiency is improved obviously.To improve efficiency fur-ther,a highly-efficient generation algorithm based on the artificial fish-swarm algorithm is proposed.The efficiency is improved by 17 times compared with that of the cycle merging algorithm.The shield has good randomness with the complexity up to 0.99bit.A generation software is developed,which can generate several complex shields,for example the parallel multi-channel shield.Afterwards,two detectors are designed to monitor the integrity of various active shield.The random-bits-flow detector is based on the comparison of random bits.It supports integrity check for an active shield which has more than 20 channels.Besides,a resistance detector is designed based on?-?analog to digital converter structure.By measuring the changes of the parasitic resistance,this circuit can detect the rerouting attack.In a 0.18?m CMOS process,the minimum discernible area is 40×40?m~2,which is 0.025%of the total protected area.The compensation methods of temperature and process deviation are also studied.Then,a compensation circuit is designed.Aiming at the data remanence of Flash memories,the data erasure strategy based on random time is studied first.By introducing random time into the execution time of an erasure operation,the correlation between the erased data and the number of residual electrons in floating gate is broken.Afterwards,an overwriting strategy is studied.A deep overwriting sequence is proposed through the simulation analyses based on the floating-gate device model.The differences in threshold voltage of floating-gate cells after using this sequence can equal to that influenced by an electron.Such differences are so tiny that the current recovery technique cannot distinguish them,making data re-covery impracticable.A fast-and-deep erasure algorithm based on the deep overwriting sequence is proposed.The erasure is achieved by destroying the integrity of files.The verification platform shows that the erasure time can be reduced by 90%for the EPCS4memory.Based on the above research,a secure memory is designed and verified.The basic architecture of the secure memory is proposed.Several key modules,such as the active shield and the low-power RC oscillator,are designed.Finally,this memory is typed out in a 0.18?m CMOS process.The performance tests of the memory are executed based on the verification software.The secure memory can detect several physical attacks,such as the drilling attack with the aperture larger than 0.8mm and the optical fault in-jection attack with the light intensity higher than 1Lux.The whole data can be erased within a short time,which guarantees the data security.