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chg: 'lf nexwatch demod' - now detects type, and show parity /chksum

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This commit is contained in:
iceman1001 2020-05-11 09:29:51 +02:00
parent 4d34c8d4d5
commit 9b08f7c39b
1 changed files with 30 additions and 42 deletions
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72
client/src/cmdlfnexwatch.c
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@ -180,7 +180,9 @@ int demodNexWatch(void) {
d_id |= DemodBuffer[DOFFSET + 32];
uint8_t mode = bytebits_to_byte(DemodBuffer + 72, 4);
uint8_t parity = bytebits_to_byte(DemodBuffer + 76, 4);
uint8_t chk = bytebits_to_byte(DemodBuffer + 80, 8);
// parity check
// from 32 hex id, 4 mode, descramble par (1234) -> (4231)
uint8_t xor_par = 0;
@ -194,62 +196,48 @@ int demodNexWatch(void) {
calc_parity |= (((xor_par >> 2 ) & 1) << 2);
calc_parity |= ((xor_par & 1) << 3);
uint8_t parity = bytebits_to_byte(DemodBuffer + 76, 4);
/*
Checksum:::
1. Subtract every byte from ID field using an unsigned, one byte register:
1F - 15 - A5 - 6D = 0xF6
2. Subtract BE from the result:
0xF6 - 0xBE = 3A
3. Reverse the bits of a parity nibble:
5(0101) -> (1010) A
4. Subtract the reversed parity from the result:
3A - A = 30 -> 00110000
5. Reverse the bits:
00001100 -> 0C
*/
/*
// Checksum
uint8_t calc;
calc = ((d_id >> 24) & 0xFF);
calc -= ((d_id >> 16) & 0xFF);
calc -= ((d_id >> 8) & 0xFF);
calc -= (d_id & 0xFF);
uint8_t revpar = (reflect8(calc_parity) >> 4);
PrintAndLogEx(NORMAL, "Sum: 0x%02x", calc);
typedef struct {
uint8_t magic;
char desc[10];
uint8_t chk;
} nexwatch_magic_t;
nexwatch_magic_t items[] = { {0xBE, "Quadrakey", 0}, {0x88, "Nexkey", 0} };
uint8_t a[] = {0xbe, 0xbc, 0x88, 0x86 };
for (uint8_t c=0; c < ARRAYLEN(a); c++) {
uint8_t b = calc;
b -= a[c];
PrintAndLogEx(NORMAL, "Subtract [0x%02X] : 0x%02X", a[c], b);
b -= revpar;
PrintAndLogEx(NORMAL, "Subtract revpar : 0x%02X", b);
PrintAndLogEx(NORMAL, "reversed : 0x%02X", reflect8(b));
uint8_t m_idx;
for ( m_idx = 0; m_idx < ARRAYLEN(items); m_idx++) {
uint8_t foo = calc;
foo -= items[m_idx].magic;
foo -= revpar;
foo = reflect8(foo);
items[m_idx].chk = foo;
if (foo == chk) {
break;
}
}
calc -= 0xBE;
PrintAndLogEx(NORMAL, "--after 0xBE: %02x", calc);
calc -= revpar;
PrintAndLogEx(NORMAL, "--before reverse: %02x", calc);
calc = reflect8(calc);
*/
// uint8_t chk = bytebits_to_byte(DemodBuffer + 80, 8);
// detect keytype
// output
PrintAndLogEx(SUCCESS, " NexWatch raw id : " _YELLOW_("0x%"PRIx32) , rawid);
PrintAndLogEx(SUCCESS, " 88bit id : " _YELLOW_("%"PRIu32) " " _YELLOW_("0x%"PRIx32), d_id, d_id);
PrintAndLogEx(SUCCESS, " mode : %x", mode);
PrintAndLogEx(SUCCESS, " parity : %s [%X == %X]", (parity == calc_parity) ? _GREEN_("ok") : _RED_("fail"), parity, calc_parity);
// PrintAndLogEx(NORMAL, " checksum : %02x == %02x", calc, chk);
if (m_idx < 3) {
PrintAndLogEx(SUCCESS, " checksum : %s [%X]", _GREEN_("ok"), chk);
PrintAndLogEx(SUCCESS, " Keytype : " _GREEN_("%s"), items[m_idx].desc);
} else {
PrintAndLogEx(WARNING, " checksum : %s [%X == %X]", _RED_("fail"), chk, items[m_idx].chk);
}
// bits to hex (output used for SIM/CLONE cmd)
CmdPrintDemodBuff("x");