RfidResearchGroup/proxmark3
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add: fast 8bit reversal.

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This commit is contained in:
iceman1001 2018-01-27 22:20:56 +01:00
parent 60afef3938
commit ede55a1498
5 changed files with 22 additions and 9 deletions
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2
armsrc/iso14443a.c
View file

@ -2503,7 +2503,7 @@ void ReaderMifare(bool first_try, uint8_t block, uint8_t keytype ) {
if (nt_diff == 0 && first_try)
par_low = par[0] & 0xE0; // there is no need to check all parities for other nt_diff. Parity Bits for mf_nr_ar[0..2] won't change
par_list[nt_diff] = SwapBits(par[0], 8);
par_list[nt_diff] = reflect8(par[0]);
ks_list[nt_diff] = receivedAnswer[0] ^ 0x05; // xor with NACK value to get keystream
// Test if the information is complete

11
armsrc/util.c
View file

@ -13,14 +13,19 @@ size_t nbytes(size_t nbits) {
return (nbits >> 3)+((nbits % 8) > 0);
}
uint32_t SwapBits(uint32_t value, int nrbits) {
// Swap bit order on a uint32_t value. Can be limited by 'b' just use say 8 bits reversal
// note: function clears the rest of the bits.
uint32_t SwapBits(uint32_t v, int b) {
uint32_t newvalue = 0;
for(int i = 0; i < nrbits; i++) {
newvalue ^= ((value >> i) & 1) << (nrbits - 1 - i);
for(int i = 0; i < b; i++) {
newvalue ^= ((v >> i) & 1) << (b - 1 - i);
}
return newvalue;
}
uint8_t reflect8(uint8_t b) {
return ((b * 0x80200802ULL) & 0x0884422110ULL) * 0x0101010101ULL >> 32;
}
/*
ref http://www.csm.ornl.gov/~dunigan/crc.html
Returns the value v with the bottom b [0,32] bits reflected.

4
armsrc/util.h
View file

@ -42,6 +42,10 @@
size_t nbytes(size_t nbits);
uint32_t SwapBits(uint32_t value, int nrbits);
uint32_t reflect(uint32_t v, int b);
// dedicated 8bit reversal
uint8_t reflect8(uint8_t b);
void num_to_bytes(uint64_t n, size_t len, uint8_t* dest);
uint64_t bytes_to_num(uint8_t* src, size_t len);
void rol(uint8_t *data, const size_t len);

13
client/util.c
View file

@ -729,15 +729,18 @@ void rol(uint8_t *data, const size_t len){
data[len-1] = first;
}
// Swap bit order on a uint32_t value. Can be limited by nrbits just use say 8bits reversal
// And clears the rest of the bits.
uint32_t SwapBits(uint32_t value, int nrbits) {
// Swap bit order on a uint32_t value. Can be limited by 'b' just use say 8 bits reversal
// note: function clears the rest of the bits.
uint32_t SwapBits(uint32_t v, int b) {
uint32_t newvalue = 0;
for(int i = 0; i < nrbits; i++) {
newvalue ^= ((value >> i) & 1) << (nrbits - 1 - i);
for(int i = 0; i < b; i++) {
newvalue ^= ((v >> i) & 1) << (b - 1 - i);
}
return newvalue;
}
uint8_t reflect8(uint8_t b) {
return ((b * 0x80200802ULL) & 0x0884422110ULL) * 0x0101010101ULL >> 32;
}
/*
ref http://www.csm.ornl.gov/~dunigan/crc.html
Returns the value v with the bottom b [0,32] bits reflected.

1
client/util.h
View file

@ -204,6 +204,7 @@ extern uint32_t PackBits(uint8_t start, uint8_t len, uint8_t* bits);
extern void rol(uint8_t *data, const size_t len);
extern uint32_t SwapBits(uint32_t value, int nrbits);
extern uint32_t reflect(uint32_t v, int b);
extern uint8_t reflect8(uint8_t b); // dedicated 8bit reversal
extern uint64_t HornerScheme(uint64_t num, uint64_t divider, uint64_t factor);
extern int num_CPUs(void); // number of logical CPUs