A User Centric Security Model for Tamper-Resistant Devices

C.11 Implementation Helper Classes
133 JCSystem .CLEAR_ON_DESELECT) ;
134 MessageDigest SHA256 ;
135 void Xor ( byte [ ] inputBuffer , byte c o n d i t i o n ) {
136 i f ( c o n d i t i o n == 1) {
137 for ( short i = 1 , j = 0 ; i = ( short ) 32) {
140 j = 0 ;
141 }
142 }
143 } else {
144 for ( short i = 1 ; i = FILE_SIZE) {
152 CyclicRecordReadPointer = 0 ;
153 } U t i l . arrayCopyNonAtomic ( C y c l i c S e e d F i l e , CyclicRecordReadPointer ,
154 readBuffer , ( short ) 1 , ( short )
155 (RECORD_SIZE + 1) ) ;
156 CyclicRecordReadPointer = ( short ) ( ( short ) CyclicRecordReadPointer
157 + RECORD_SIZE) ;
158 }
159 private void C y c l i c S e e d F i l e W r i t e ( byte [ ] w r i t e B u f f e r ) {
160 i f ( CyclicRecordWritePointer >= FILE_SIZE) {
161 CyclicRecordWritePointer = 0 ;
162 } U t i l . arrayCopyNonAtomic ( C y c l i c S e e d F i l e ,
163 CyclicRecordWritePointer , w r i t e B u f f e r ,
164 ( short ) (RECORD_SIZE + 1) , RECORD_SIZE) ;
165 Xor ( w r i t e B u f f e r , ( byte ) 0) ;
166 U t i l . arrayCopyNonAtomic ( w r i t e B u f f e r , (byte ) 1 , C y c l i c S e e d F i l e ,
167 CyclicRecordWritePointer , RECORD_SIZE) ;
168 CyclicRecordWritePointer = ( short ) ( ( short )
169 CyclicRecordWritePointer +
170 RECORD_SIZE) ;
171 }
172 private void Adjuster ( i n p u t B u f f e r ) {
173 for ( short i = 0 ; i < 1 6 ; i ++) {
174 i n p u t B u f f e r [ ( short ) i ] = ( byte ) ( B u f f e r [ ( short ) i ] ^ B u f f e r [ ( short ) (31
175 −i ) ] ) ;
176 }
177 }
178
179
180 private PrngSHA256 ( byte bArray [ ] , short bOffset , byte bLength ) {
181 SHA256 = MessageDigest . g e t I n s t a n c e ( MessageDigest .ALG_SHA_256,
182 f a l s e ) ;
183 r e g i s t e r ( ) ;
448