X-Git-Url: https://git.distorted.org.uk/u/mdw/catacomb/blobdiff_plain/898a4e2555438ff8adb08b4d82690d08715e1048..b817bfc642225b8c3c0b6a7e42d1fb949b61a606:/gf.h

diff --git a/gf.h b/gf.h
index fba801c..2429e95 100644
--- a/gf.h
+++ b/gf.h
@@ -1,6 +1,6 @@
 /* -*-c-*-
  *
- * $Id: gf.h,v 1.3 2004/03/27 17:54:11 mdw Exp $
+ * $Id: gf.h,v 1.4 2004/04/08 01:36:15 mdw Exp $
  *
  * Arithmetic on binary polynomials
  *
@@ -27,20 +27,6 @@
  * MA 02111-1307, USA.
  */
 
-/*----- Revision history --------------------------------------------------* 
- *
- * $Log: gf.h,v $
- * Revision 1.3  2004/03/27 17:54:11  mdw
- * Standard curves and curve checking.
- *
- * Revision 1.2  2004/03/21 22:52:06  mdw
- * Merge and close elliptic curve branch.
- *
- * Revision 1.1.2.1  2004/03/21 22:39:46  mdw
- * Elliptic curves on binary fields work.
- *
- */
-
 #ifndef CATACOMB_GF_H
 #define CATACOMB_GF_H
 
@@ -130,6 +116,21 @@ extern int gf_irreduciblep(mp */*f*/);
 extern void gf_gcd(mp **/*gcd*/, mp **/*xx*/, mp **/*yy*/,
 		   mp */*a*/, mp */*b*/);
 
+/* -- @gf_modinv@ --- *
+ *
+ * Arguments:	@mp *d@ = destination
+ *		@mp *x@ = argument
+ *		@mp *p@ = modulus
+ *
+ * Returns:	The inverse %$x^{-1} \bmod p$%.
+ *
+ * Use:		Computes a modular inverse, the catch being that the
+ *		arguments and results are binary polynomials.  An assertion
+ *		fails if %$p$% has no inverse.
+ */
+
+extern mp *gf_modinv(mp */*d*/, mp */*x*/, mp */*p*/);
+
 /*----- That's all, folks -------------------------------------------------*/
 
 #ifdef __cplusplus