ifndef SIGCLD
define SIGCLD SIGCHLD
endif
solved

2.src/mont/fp_montgomery_reduce.c:514:15: error: unknown register name '%cc' in
asm
INNERMUL8;

We should also have a TFM implementation of the sqrtmod_prime() function as done for LTM in libtom/libtommath#33

@lvc would you mind adding tomsfastmath to your tool please, including develop?

If neither ENDIAN_BIG nor ENDIAN_LITTLE is defined, the following code is executed in fp_read_unsigned_bin

#else
  /* read the bytes in */
  for (; c > 0; c--) {
     fp_mul_2d (a, 8, a);
     a->dp[0] |= *b++;
     a->used += 1;
  }
#endif

This will overflow a->dp array if c is large enough. I implemented a local change by having fp_read_unsigned_bin return a failure status in such case but I see now that the code above seems to truncate the input.

Hi Tom,
I am trying to perform left and right shift x digits via the functions fp_lshd and fp_rshd:

  fp_int a;

  fp_set(&a, 60); fp_print("", "\n", a, 10);
  fp_lshd(&a, 1); fp_print("", "\n", a, 10);

  fp_set(&a, 60); fp_print("", "\n", a, 10);
  fp_rshd(&a, 1); fp_print("", "\n", a, 10);

  printf("%d\n", (60 << 1));
  printf("%d\n", (60 >> 1));

The output is:

60
1106804644422573096960
60
0
120
30

fp_print defined as follows:

void fp_print(const char *start, const char *end, const fp_int u, int base)
{
  int size_u;
  fp_radix_size((fp_int *)&u, base, &size_u);
  char *buf_u = malloc(size_u);
  fp_toradix_n((fp_int *)&u, buf_u, base, size_u);
  printf("%s%s%s", start, buf_u, end);
}

Am I wrong using it?

Obviously my use case is for larger numbers

fp_sqr does not handle case when parameter a = 00....00

When a=00.....00 the result b is not updated.

Adding the following code after y = A->used; seems to resolve this
if (y==0) {
B->used = 0;
goto clean;
}

imo everybody intending to do any real-life work with tomsfastmath will require this function to import his binary private keys etc. it should be mentioned right after fp_init() and fp_set(). i spent about half an hour to search for this functionality in both tfm pdf and ltm pdf without success, and only found out by digging through the ltc rsa code.

Hi Tom

fp_iseven() appears a little incorrect to me, and it should be the following IMO:

diff --git a/src/headers/tfm.h b/src/headers/tfm.h
index 0d1dbf1..6f00c08 100644
--- a/src/headers/tfm.h
+++ b/src/headers/tfm.h
@@ -335,7 +335,7 @@ const char *fp_ident(void);
 
 /* zero/even/odd ? */
 #define fp_iszero(a) (((a)->used == 0) ? FP_YES : FP_NO)
-#define fp_iseven(a) (((a)->used >= 0 && (((a)->dp[0] & 1) == 0)) ? FP_YES : FP_NO)
+#define fp_iseven(a) (((a)->used == 0 || (((a)->dp[0] & 1) == 0)) ? FP_YES : FP_NO)
 #define fp_isodd(a)  (((a)->used > 0  && (((a)->dp[0] & 1) == 1)) ? FP_YES : FP_NO)
 
 /* set to a small digit */

Setting M to "2 ^ 4423 - 1", then "exptmod(3,M,M)" should give '3'.

The current code returns 1 from fp_exptmod, presumably because the modulus is so large.

#include "stdio.h"
#include "tfm.h"

void s_mp_sqr(fp_int *x)
{
	fp_int tmp;
	fp_init(&tmp);
	fp_sqr(x,&tmp);
	fp_copy(&tmp, x);
}

void fp_expt(fp_int *a, fp_int *b, fp_int *c)
{
	fp_int   s, x;
	fp_digit d;
	int      dig, bit;


	if (b->sign == FP_NEG)
		return ;

	fp_init(&s);

	fp_set(&s, 1);

	fp_init_copy(&x, a);

	/* Loop over low-order digits in ascending order */
	for(dig = 0; dig < (b->used - 1); dig++) {
		d = b->dp[dig];

		/* Loop over bits of each non-maximal digit */
		fp_int tmp;
		for(bit = 0; bit < DIGIT_BIT; bit++) {
			if(d & 1) {
				s.sign = FP_ZPOS;
				x.sign = FP_ZPOS;
				fp_init(&tmp);
				fp_mul(&s, &x, &tmp);
				fp_copy(&tmp, &s);
			}

			d >>= 1;

			s_mp_sqr(&x);
		}
	}

	/* Consider now the last digit... */
	d = b->dp[dig];

	fp_int tmp;
	while(d) {
		if(d & 1) {
			s.sign = x.sign = FP_ZPOS;
			fp_init(&tmp);
			fp_mul(&s, &x, &tmp);
			fp_copy(&tmp, &s);
		}

		d >>= 1;

		s_mp_sqr(&x);
	}

	if(fp_iseven(b))
		s.sign = FP_ZPOS;
	else
		s.sign = a->sign;

	fp_copy(&s, c);

} /* end fp_expt() */

int main(int argc, char ** argv )
{
	fp_int a,b,c,d;
	fp_init(&a);
	fp_init(&b);
	fp_init(&c);
	fp_init(&d);

	fp_set(&a, 3);
	fp_set(&b, 2);
	fp_set(&c, 4423);
	fp_expt(&b, &c, &d);
	fp_copy(&d, &b);

	fp_init(&d);
	int rc = fp_exptmod(&a, &b, &b, &d);

	int size=0;
	fp_radix_size(&d, 10, &size);
	char * outstr = (char *) malloc(size+1);
	fp_toradix(&d, outstr, 10);
	outstr[size] = '\0';
	printf("rc = %d, result (should be 3): %s\n", rc, outstr);
	return 0;
}

One thing we found productive is TFM can be fairly easily ported to be variable precision. This in turn saves a lot of memory at a small (trivial) cost in performance.

I can't contribute code (right now) but it's something that is worth looking into. It would also make FP_MAX_SIZE obsolete.

LibTomCrypt and LibTomMath come with mingw makefiles, thanks for that. Please add this makefile also for TomsFastMath.

I'm trying to package Tomsfastmath for Homebrew, but the latest release (0.13.1) was published in April 2017, and requires patching in the Homebrew formula to build. There have also been a lot of changes since Tomsfastmath 0.13.1, in addition to a license change. Therefore, it would be great if you would publish a new release.