X-Git-Url: https://git.zerfleddert.de/cgi-bin/gitweb.cgi/proxmark3-svn/blobdiff_plain/49dc1d0a9eafdb1e369ead88c3c8882bc6959a17..c71c5ee1567c08b9819b3e9733ccb81e875bfca3:/common/legic_prng.c diff --git a/common/legic_prng.c b/common/legic_prng.c index 322429ad..93229251 100644 --- a/common/legic_prng.c +++ b/common/legic_prng.c @@ -6,36 +6,36 @@ // LEFIC's obfuscation function //----------------------------------------------------------------------------- -#include "../include/legic_prng.h" +#include "legic_prng.h" struct lfsr { - uint8_t a; - uint8_t b; - uint32_t c; + uint8_t a; + uint8_t b; + uint32_t c; } lfsr; void legic_prng_init(uint8_t init) { - lfsr.c = 0; - lfsr.a = init; - if(init == 0) /* hack to get a always 0 keystream */ - lfsr.b = 0; - else - lfsr.b = (init << 1) | 1; + lfsr.a = init; + lfsr.b = 0; // hack to get a always 0 keystream + lfsr.c = 0; + if(init) + lfsr.b = (init << 1) | 1; } void legic_prng_forward(int count) { - lfsr.c += count; - while(count--) { - lfsr.a = lfsr.a >> 1 | (lfsr.a ^ lfsr.a >> 6) << 6; - lfsr.b = lfsr.b >> 1 | (lfsr.b ^ lfsr.b >> 2 ^ lfsr.b >> 3 ^ lfsr.b >> 7) << 7; - } + lfsr.c += count; + while(count--) { + // According: http://www.proxmark.org/forum/viewtopic.php?pid=5437#p5437 + lfsr.a = (lfsr.a >> 1 | (lfsr.a ^ lfsr.a >> 6) << 6) & 0x7F; + lfsr.b = lfsr.b >> 1 | (lfsr.b ^ lfsr.b >> 2 ^ lfsr.b >> 3 ^ lfsr.b >> 7) << 7; + } } -int legic_prng_count() { - return lfsr.c; +uint32_t legic_prng_count() { + return lfsr.c; } uint8_t legic_prng_get_bit() { - uint8_t idx = 7 - ( (lfsr.a & 4) | (lfsr.a >> 2 & 2) | (lfsr.a >> 4 & 1) ); - return lfsr.b >> idx & 1; -} + uint8_t idx = 7 - ( (lfsr.a & 4) | (lfsr.a >> 2 & 2) | (lfsr.a >> 4 & 1) ); + return lfsr.b >> idx & 1; +} \ No newline at end of file