X-Git-Url: https://git.distorted.org.uk/~mdw/catacomb/blobdiff_plain/0f00dc4c8eb47e67bc0f148c2dd109f73a451e0a..6a024d24d97cb5d42c0091571735475b849f59f4:/math/strongprime.h

diff --git a/math/strongprime.h b/math/strongprime.h
index 6f39f500..14ad39e4 100644
--- a/math/strongprime.h
+++ b/math/strongprime.h
@@ -60,7 +60,14 @@
  * Use:		Sets up for a strong prime search, so that primes with
  *		particular properties can be found.  It's probably important
  *		to note that the number left in the filter context @f@ is
- *		congruent to 2 (mod 4).
+ *		congruent to 2 (mod 4); that the jump value is twice the
+ *		product of two large primes; and that the starting point is
+ *		at least %$3 \cdot 2^{N-2}$%.  (Hence, if you multiply two
+ *		such numbers, the product is at least
+ *
+ *			%$9 \cdot 2^{2N-4} > 2^{2N-1}$%
+ *
+ *		i.e., it will be (at least) a %$2 N$%-bit value.
  */
 
 extern mp *strongprime_setup(const char */*name*/, mp */*d*/, pfilt */*f*/,
@@ -85,9 +92,6 @@ extern mp *strongprime_setup(const char */*name*/, mp */*d*/, pfilt */*f*/,
  *		  * %$p - 1$% has a large prime factor %$r$%,
  *		  * %$p + 1$% has a large prime factor %$s$%, and
  *		  * %$r - 1$% has a large prime factor %$t$%.
- *
- *		The numbers produced may be slightly larger than requested,
- *		by a few bits.
  */
 
 extern mp *strongprime(const char */*name*/, mp */*d*/, unsigned /*nbits*/,