数据擦除算法
====================================================================
DoD 5220.22-M算法:
char dod [7]；
typedef struct
{
int length;
char* s;
} dwipe_pattern_t
}
覆盖填充七次，定义dod元素值
dwipe_pattern_t patterns [] =
{
{ 1, &dod[0] }, /* Pass 1: A random character. */
{ 1, &dod[1] }, /* Pass 2: The bitwise complement of pass 1. */
{ -1, "" }, /* Pass 3: A random stream. */
{ 1, &dod[3] }, /* Pass 4: A random character. */
{ 1, &dod[4] }, /* Pass 5: A random character. */
{ 1, &dod[5] }, /* Pass 6: The bitwise complement of pass 5. */
{ -1, "" }, /* Pass 7: A random stream. */
{ 0, NULL }
};
随机读取元素存放入dod
r = read( c->entropy_fd, &dod, sizeof( dod ) );
把dod第1个元素反补后放入dod[1]
dod[1] = ~ dod[0];
把dod第4个元素反补后放入dod[5]
dod[5] = ~ dod[4];
当patterns[i].length == 0,什么都不做 //{ 0, NULL }
当patterns[i].length > 0，把dod中相应某个元素填充磁盘区域，直到填满 // 如{ 1, &dod[0] },{ 1, &dod[1] }
当patterns[i].length < 0，调用用随机数填充 //{ -1, "" }
====================================================================
DoD Short算法:
覆盖填充三次
dwipe_pattern_t patterns [] =
{
{ 1, &dod[0] }, /* Pass 1: A random character. */
{ 1, &dod[1] }, /* Pass 2: The bitwise complement of pass 1. */
{ -1, "" }, /* Pass 3: A random stream. */
{ 0, NULL }
};
随机读取元素存放入dod
r = read( c->entropy_fd, &dod, sizeof( dod ) );
把dod第1个元素反补后放入dod[1]
dod[1] = ~ dod[0];
当patterns[i].length == 0,什么都不做 //{ 0, NULL }
当patterns[i].length > 0，把dod中相应某个元素填充磁盘区域，直到填满 // 如{ 1, &dod[0] },{ 1, &dod[1] }
当patterns[i].length < 0，调用用随机数填充 //{ -1, "" }
====================================================================
Gutmann算法：
覆盖填充35次
dwipe_pattern_t book [] =
{
{ -1, "" }, /* Random pass. */
{ -1, "" }, /* Random pass. */
{ -1, "" }, /* Random pass. */
{ -1, "" }, /* Random pass. */
{ 3, "/x55/x55/x55" }, /* Static pass: 0x555555 01010101 01010101 01010101 */
{ 3, "/xAA/xAA/xAA" }, /* Static pass: 0XAAAAAA 10101010 10101010 10101010 */
{ 3, "/x92/x49/x24" }, /* Static pass: 0x924924 10010010 01001001 00100100 */
{ 3, "/x49/x24/x92" }, /* Static pass: 0x492492 01001001 00100100 10010010 */
{ 3, "/x24/x92/x49" }, /* Static pass: 0x249249 00100100 10010010 01001001 */
{ 3, "/x00/x00/x00" }, /* Static pass: 0x000000 00000000 00000000 00000000 */
{ 3, "/x11/x11/x11" }, /* Static pass: 0x111111 00010001 00010001 00010001 */
{ 3, "/x22/x22/x22" }, /* Static pass: 0x222222 00100010 00100010 00100010 */
{ 3, "/x33/x33/x33" }, /* Static pass: 0x333333 00110011 00110011 00110011 */
{ 3, "/x44/x44/x44" }, /* Static pass: 0x444444 01000100 01000100 01000100 */
{ 3, "/x55/x55/x55" }, /* Static pass: 0x555555 01010101 01010101 01010101 */
{ 3, "/x66/x66/x66" }, /* Static pass: 0x666666 01100110 01100110 01100110 */
{ 3, "/x77/x77/x77" }, /* Static pass: 0x777777 01110111 01110111 01110111 */
{ 3, "/x88/x88/x88" }, /* Static pass: 0x888888 10001000 10001000 10001000 */
{ 3, "/x99/x99/x99" }, /* Static pass: 0x999999 10011001 10011001 10011001 */
{ 3, "/xAA/xAA/xAA" }, /* Static pass: 0xAAAAAA 10101010 10101010 10101010 */
{ 3, "/xBB/xBB/xBB" }, /* Static pass: 0xBBBBBB 10111011 10111011 10111011 */
{ 3, "/xCC/xCC/xCC" }, /* Static pass: 0xCCCCCC 11001100 11001100 11001100 */
{ 3, "/xDD/xDD/xDD" }, /* Static pass: 0xDDDDDD 11011101 11011101 11011101 */
{ 3, "/xEE/xEE/xEE" }, /* Static pass: 0xEEEEEE 11101110 11101110 11101110 */
{ 3, "/xFF/xFF/xFF" }, /* Static pass: 0xFFFFFF 11111111 11111111 11111111 */
{ 3, "/x92/x49/x24" }, /* Static pass: 0x924924 10010010 01001001 00100100 */
{ 3, "/x49/x24/x92" }, /* Static pass: 0x492492 01001001 00100100 10010010 */
{ 3, "/x24/x92/x49" }, /* Static pass: 0x249249 00100100 10010010 01001001 */
{ 3, "/x6D/xB6/xDB" }, /* Static pass: 0x6DB6DB 01101101 10110110 11011011 */
{ 3, "/xB6/xDB/x6D" }, /* Static pass: 0xB6DB6D 10110110 11011011 01101101 */
{ 3, "/xDB/x6D/xB6" }, /* Static pass: 0XDB6DB6 11011011 01101101 10110110 */
{ -1, "" }, /* Random pass. */
{ -1, "" }, /* Random pass. */
{ -1, "" }, /* Random pass. */
{ -1, "" }, /* Random pass. */
{ 0, NULL }
};
当patterns[i].length == 0,什么都不做 //{ 0, NULL }
当patterns[i].length > 0，把dod中相应十六进制填充磁盘区域，直到填满 // 如{ 1, "/xB6/xDB/x6D" },{ 3, "/xDB/x6D/xB6" },
当patterns[i].length < 0，调用用随机数填充 //{ -1, "" }