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84 lines
3.4 KiB
C
84 lines
3.4 KiB
C
#ifndef HITAG2_H
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#define HITAG2_H
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#include <stdint.h>
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#include <stdbool.h>
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// as the HITAG2 original implementation, with some minor changes
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#define i4(x,a,b,c,d) ((uint32_t)((((x)>>(a))&1)<<3)|(((x)>>(b))&1)<<2|(((x)>>(c))&1)<<1|(((x)>>(d))&1))
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#define f(state) ((uint32_t)((0xdd3929b >> ( (((0x3c65 >> i4(state, 2, 3, 5, 6) ) & 1) <<4) \
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| ((( 0xee5 >> i4(state, 8,12,14,15) ) & 1) <<3) \
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| ((( 0xee5 >> i4(state,17,21,23,26) ) & 1) <<2) \
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| ((( 0xee5 >> i4(state,28,29,31,33) ) & 1) <<1) \
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| (((0x3c65 >> i4(state,34,43,44,46) ) & 1) ))) & 1))
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#define get_bit(n, word) ((word >> (n)) & 1)
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/*
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* Hitag Crypto support macros
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* These macros reverse the bit order in a byte, or *within* each byte of a
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* 16 , 32 or 64 bit unsigned integer. (Not across the whole 16 etc bits.)
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*/
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#define rev8(X) ((((X) >> 7) &1) + (((X) >> 5) &2) + (((X) >> 3) &4) \
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+ (((X) >> 1) &8) + (((X) << 1) &16) + (((X) << 3) &32) \
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+ (((X) << 5) &64) + (((X) << 7) &128) )
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#define rev16(X) (rev8 (X) + (rev8 (X >> 8) << 8))
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#define rev32(X) (rev16(X) + (rev16(X >> 16) << 16))
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#define rev64(X) (rev32(X) + (rev32(X >> 32) << 32))
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typedef struct {
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uint64_t shiftreg; // naive shift register, required for nonlinear fn input
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uint64_t lfsr; // fast lfsr, used to make software faster
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} Hitag_State;
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// return a single bit from a value
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int bitn(uint64_t x, int bit);
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// the sub-function R that rollback depends upon
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int fnR(uint64_t x);
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// the three filter sub-functions that feed fnf
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int fa(unsigned int i);
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int fb(unsigned int i);
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// the filter function that generates a bit of output from the prng state
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int fnf(uint64_t s);
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// macros to pick out 4 bits in various patterns of 1s & 2s & make a new number
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#define pickbits2_2(S, A, B) ( ((S >> A) & 3) | ((S >> (B - 2)) & 0xC) )
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#define pickbits1x4(S, A, B, C, D) ( ((S >> A) & 1) | ((S >> (B - 1)) & 2) | ((S >> (C - 2)) & 4) | ((S >> (D - 3)) & 8) )
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#define pickbits1_1_2(S, A, B, C) ( ((S >> A) & 1) | ((S >> (B - 1)) & 2) | ((S >> (C - 2)) & 0xC) )
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#define pickbits2_1_1(S, A, B, C) ( ((S >> A) & 3) | ((S >> (B - 2)) & 4) | ((S >> (C - 3)) & 8) )
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#define pickbits1_2_1(S, A, B, C) ( ((S >> A) & 1) | ((S >> (B - 1)) & 6) | ((S >> (C - 3)) & 8) )
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uint32_t hitag2_crypt(uint64_t x);
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/*
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* Return up to 32 crypto bits.
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* Last bit is in least significant bit, earlier bits are shifted left.
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* Note that the Hitag transmission protocol is least significant bit,
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* so we may want to change this, or add a function, that returns the
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* crypto output bits in the other order.
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*
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* Parameters:
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* Hitag_State* pstate - in/out, internal cipher state after initialisation
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* uint32_t steps - number of bits requested, (capped at 32)
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*/
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uint32_t hitag2_nstep(Hitag_State *pstate, uint32_t steps);
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/*
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* Parameters:
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* Hitag_State* pstate - output, internal state after initialisation
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* uint64_t sharedkey - 48 bit key shared between reader & tag
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* uint32_t serialnum - 32 bit tag serial number
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* uint32_t initvector - 32 bit random IV from reader, part of tag authentication
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*/
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void hitag2_init(Hitag_State *pstate, uint64_t sharedkey, uint32_t serialnum, uint32_t initvector);
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// try_state
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bool try_state(uint64_t s, uint32_t uid, uint32_t aR2, uint32_t nR1, uint32_t nR2, uint64_t *key);
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#endif // HITAG2_H
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