1 files changed, 105 insertions, 0 deletions
diff --git a/libtommath/bn_mp_is_square.c b/libtommath/bn_mp_is_square.c
new file mode 100644
index 0000000..969d237
--- /dev/null
+++ b/libtommath/bn_mp_is_square.c
@@ -0,0 +1,105 @@
+#include <tommath.h>
+#ifdef BN_MP_IS_SQUARE_C
+/* LibTomMath, multiple-precision integer library -- Tom St Denis
+ *
+ * LibTomMath is a library that provides multiple-precision
+ * integer arithmetic as well as number theoretic functionality.
+ *
+ * The library was designed directly after the MPI library by
+ * Michael Fromberger but has been written from scratch with
+ * additional optimizations in place.
+ *
+ * The library is free for all purposes without any express
+ * guarantee it works.
+ *
+ * Tom St Denis, tomstdenis@iahu.ca, http://math.libtomcrypt.org
+ */
+
+/* Check if remainders are possible squares - fast exclude non-squares */
+static const char rem_128[128] = {
+ 0, 0, 1, 1, 0, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1,
+ 0, 0, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1,
+ 1, 0, 1, 1, 0, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1,
+ 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1,
+ 0, 0, 1, 1, 0, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1,
+ 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1,
+ 1, 0, 1, 1, 0, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1,
+ 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1
+};
+
+static const char rem_105[105] = {
+ 0, 0, 1, 1, 0, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1,
+ 0, 0, 1, 1, 1, 1, 0, 1, 1, 1, 0, 1, 1, 1, 1,
+ 0, 1, 1, 1, 1, 1, 0, 1, 1, 0, 1, 1, 1, 1, 1,
+ 1, 0, 1, 1, 0, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1,
+ 0, 1, 1, 1, 0, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1,
+ 1, 1, 1, 1, 0, 1, 0, 1, 1, 0, 0, 1, 1, 1, 1,
+ 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1
+};
+
+/* Store non-zero to ret if arg is square, and zero if not */
+int mp_is_square(mp_int *arg,int *ret) 
+{
+  int           res;
+  mp_digit      c;
+  mp_int        t;
+  unsigned long r;
+
+  /* Default to Non-square :) */
+  *ret = MP_NO; 
+
+  if (arg->sign == MP_NEG) {
+    return MP_VAL;
+  }
+
+  /* digits used?  (TSD) */
+  if (arg->used == 0) {
+     return MP_OKAY;
+  }
+
+  /* First check mod 128 (suppose that DIGIT_BIT is at least 7) */
+  if (rem_128[127 & DIGIT(arg,0)] == 1) {
+     return MP_OKAY;
+  }
+
+  /* Next check mod 105 (3*5*7) */
+  if ((res = mp_mod_d(arg,105,&c)) != MP_OKAY) {
+     return res;
+  }
+  if (rem_105[c] == 1) {
+     return MP_OKAY;
+  }
+
+
+  if ((res = mp_init_set_int(&t,11L*13L*17L*19L*23L*29L*31L)) != MP_OKAY) {
+     return res;
+  }
+  if ((res = mp_mod(arg,&t,&t)) != MP_OKAY) {
+     goto ERR;
+  }
+  r = mp_get_int(&t);
+  /* Check for other prime modules, note it's not an ERROR but we must
+   * free "t" so the easiest way is to goto ERR.  We know that res
+   * is already equal to MP_OKAY from the mp_mod call 
+   */ 
+  if ( (1L<<(r%11)) & 0x5C4L )             goto ERR;
+  if ( (1L<<(r%13)) & 0x9E4L )             goto ERR;
+  if ( (1L<<(r%17)) & 0x5CE8L )            goto ERR;
+  if ( (1L<<(r%19)) & 0x4F50CL )           goto ERR;
+  if ( (1L<<(r%23)) & 0x7ACCA0L )          goto ERR;
+  if ( (1L<<(r%29)) & 0xC2EDD0CL )         goto ERR;
+  if ( (1L<<(r%31)) & 0x6DE2B848L )        goto ERR;
+
+  /* Final check - is sqr(sqrt(arg)) == arg ? */
+  if ((res = mp_sqrt(arg,&t)) != MP_OKAY) {
+     goto ERR;
+  }
+  if ((res = mp_sqr(&t,&t)) != MP_OKAY) {
+     goto ERR;
+  }
+
+  *ret = (mp_cmp_mag(&t,arg) == MP_EQ) ? MP_YES : MP_NO;
+ERR:mp_clear(&t);
+  return res;
+}
+#endif