123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103 |
- /*
- * File: dclxvi-20130329/scalar.c
- * Author: Ruben Niederhagen, Peter Schwabe
- * Public Domain
- */
- #include <stdio.h>
- #include <stdlib.h>
- #include <assert.h>
- #include "scalar.h"
- void scalar_setrandom(scalar_t rop, const scalar_t bound)
- {
- int i;
- FILE *urand = fopen("/dev/urandom", "r");
- if (urand == NULL)
- {
- fprintf(stderr, "Could not open device file /dev/urandom");
- exit(1);
- }
- do
- {
- for(i=0;i<32;i++)
- i[(unsigned char*)rop] = fgetc(urand);
- }
- while(!scalar_lt_vartime(rop,bound));
- fclose(urand);
- }
- void scalar_set_lluarray(scalar_t rop, unsigned long long v[4])
- {
- int i;
- for(i=0;i<4;i++) rop[i] = v[i];
- }
- int scalar_getbit(const scalar_t s, unsigned int pos)
- {
- assert(pos < 256);
- return (s[pos >> 6] >> (pos & 0x3f)) & 1;
- }
- // Returns the position of the most significant set bit
- int scalar_scanb(const scalar_t s)
- {
- int i;
- unsigned int pos = 0;
- for(i=255;i>0;i--)
- if(scalar_getbit(s,i) && pos == 0) pos = i;
- return pos;
- }
- int scalar_iszero_vartime(const scalar_t s)
- {
- return ((s[0] | s[1] | s[2] | s[3]) == 0);
- }
- void scalar_window4(signed char r[65], const scalar_t s)
- {
- char carry;
- int i;
- for(i=0;i<16;i++)
- r[i] = (s[0] >> (4*i)) & 15;
- for(i=0;i<16;i++)
- r[i+16] = (s[1] >> (4*i)) & 15;
- for(i=0;i<16;i++)
- r[i+32] = (s[2] >> (4*i)) & 15;
- for(i=0;i<16;i++)
- r[i+48] = (s[3] >> (4*i)) & 15;
- /* Making it signed */
- carry = 0;
- for(i=0;i<64;i++)
- {
- r[i] += carry;
- r[i+1] += r[i] >> 4;
- r[i] &= 15;
- carry = r[i] >> 3;
- r[i] -= carry << 4;
- }
- r[64] = carry;
- }
- // Returns 1 if a < b, 0 otherwise
- int scalar_lt_vartime(const scalar_t a, const scalar_t b)
- {
- if(a[3] < b[3]) return 1;
- if(a[3] > b[3]) return 0;
- if(a[2] < b[2]) return 1;
- if(a[2] > b[2]) return 0;
- if(a[1] < b[1]) return 1;
- if(a[1] > b[1]) return 0;
- if(a[0] < b[0]) return 1;
- if(a[0] > b[0]) return 0;
- return 0;
- }
- void scalar_print(FILE *fh, const scalar_t t)
- {
- int i;
- for(i=3;i>=0;i--)
- fprintf(fh, "%llx", t[i]);
- }
|