diff --git a/library/ecp.c b/library/ecp.c
index 59d399a69..2eb57fa97 100644
--- a/library/ecp.c
+++ b/library/ecp.c
@@ -1109,61 +1109,53 @@ cleanup:
 
 /*
  * Point doubling R = 2 P, Jacobian coordinates with general A
+ *
  * http://www.hyperelliptic.org/EFD/g1p/auto-code/shortw/jacobian/doubling/dbl-2007-bl.op3
+ * with heavy variable renaming, some reordering and one minor modification
+ * (a = 2 * b, c = d - 2a replaced with c = d, c = c - b, c = c - b)
+ * in order to use a lot less intermediate variables (6 vs 25).
  */
 static int ecp_double_jac_gen( const ecp_group *grp, ecp_point *R,
                                const ecp_point *P )
 {
     int ret;
-    mpi XX, YY, YYYY, ZZ, t0, t1, t2, t3, S, t4, t5, t6, M, t7, t8, T, X3, t9,
-        t10, t11, Y3, t12, t13, t14, Z3;
+    mpi T1, T2, T3, X3, Y3, Z3;
 
-    mpi_init( &XX ); mpi_init( &YY ); mpi_init( &YYYY ); mpi_init( &ZZ );
-    mpi_init( &t0 ); mpi_init( &t1 ); mpi_init( &t2 ); mpi_init( &t3 );
-    mpi_init( &S ); mpi_init( &t4 ); mpi_init( &t5 ); mpi_init( &t6 );
-    mpi_init( &M ); mpi_init( &t7 ); mpi_init( &t8 ); mpi_init( &T );
-    mpi_init( &X3 ); mpi_init( &t9 ); mpi_init( &t10 ); mpi_init( &t11 );
-    mpi_init( &Y3 ); mpi_init( &t12 ); mpi_init( &t13 ); mpi_init( &t14 );
-    mpi_init( &Z3 );
+    mpi_init( &T1 ); mpi_init( &T2 ); mpi_init( &T3 );
+    mpi_init( &X3 ); mpi_init( &Y3 ); mpi_init( &Z3 );
 
-    MPI_CHK( mpi_mul_mpi( &XX,      &P->X,  &P->X   ) ); MOD_MUL( XX );
-    MPI_CHK( mpi_mul_mpi( &YY,      &P->Y,  &P->Y   ) ); MOD_MUL( YY );
-    MPI_CHK( mpi_mul_mpi( &YYYY,    &YY,    &YY     ) ); MOD_MUL( YYYY );
-    MPI_CHK( mpi_mul_mpi( &ZZ,      &P->Z,  &P->Z   ) ); MOD_MUL( ZZ );
-    MPI_CHK( mpi_add_mpi( &t0,      &P->X,  &YY     ) ); MOD_ADD( t0 );
-    MPI_CHK( mpi_mul_mpi( &t1,      &t0,    &t0     ) ); MOD_MUL( t1 );
-    MPI_CHK( mpi_sub_mpi( &t2,      &t1,    &XX     ) ); MOD_SUB( t2 );
-    MPI_CHK( mpi_sub_mpi( &t3,      &t2,    &YYYY   ) ); MOD_SUB( t3 );
-    MPI_CHK( mpi_mul_int( &S,       &t3,    2       ) ); MOD_ADD( S  );
-    MPI_CHK( mpi_mul_mpi( &t4,      &ZZ,    &ZZ     ) ); MOD_MUL( t4 );
-    MPI_CHK( mpi_mul_mpi( &t5,      &t4,    &grp->A ) ); MOD_MUL( t5 );
-    MPI_CHK( mpi_mul_int( &t6,      &XX,    3       ) ); MOD_ADD( t6 );
-    MPI_CHK( mpi_add_mpi( &M,       &t6,    &t5     ) ); MOD_ADD( M  );
-    MPI_CHK( mpi_mul_mpi( &t7,      &M,     &M      ) ); MOD_MUL( t7 );
-    MPI_CHK( mpi_mul_int( &t8,      &S,     2       ) ); MOD_ADD( t8 );
-    MPI_CHK( mpi_sub_mpi( &T,       &t7,    &t8     ) ); MOD_SUB( T  );
-    MPI_CHK( mpi_copy( &X3, &T ) );
-    MPI_CHK( mpi_sub_mpi( &t9,      &S,     &T      ) ); MOD_SUB( t9 );
-    MPI_CHK( mpi_mul_int( &t10,     &YYYY,  8       ) ); MOD_ADD( t10 );
-    MPI_CHK( mpi_mul_mpi( &t11,     &M,     &t9     ) ); MOD_MUL( t11 );
-    MPI_CHK( mpi_sub_mpi( &Y3,      &t11,   &t10    ) ); MOD_SUB( Y3 );
-    MPI_CHK( mpi_add_mpi( &t12,     &P->Y,  &P->Z   ) ); MOD_ADD( t12 );
-    MPI_CHK( mpi_mul_mpi( &t13,     &t12,   &t12    ) ); MOD_MUL( t13 );
-    MPI_CHK( mpi_sub_mpi( &t14,     &t13,   &YY     ) ); MOD_SUB( t14 );
-    MPI_CHK( mpi_sub_mpi( &Z3,      &t14,   &ZZ     ) ); MOD_SUB( Z3 );
+    MPI_CHK( mpi_mul_mpi( &T3,  &P->X,  &P->X   ) ); MOD_MUL( T3 );
+    MPI_CHK( mpi_mul_mpi( &T2,  &P->Y,  &P->Y   ) ); MOD_MUL( T2 );
+    MPI_CHK( mpi_mul_mpi( &Y3,  &T2,    &T2     ) ); MOD_MUL( Y3 );
+    MPI_CHK( mpi_add_mpi( &X3,  &P->X,  &T2     ) ); MOD_ADD( X3 );
+    MPI_CHK( mpi_mul_mpi( &X3,  &X3,    &X3     ) ); MOD_MUL( X3 );
+    MPI_CHK( mpi_sub_mpi( &X3,  &X3,    &Y3     ) ); MOD_SUB( X3 );
+    MPI_CHK( mpi_sub_mpi( &X3,  &X3,    &T3     ) ); MOD_SUB( X3 );
+    MPI_CHK( mpi_mul_int( &T1,  &X3,    2       ) ); MOD_ADD( T1 );
+    MPI_CHK( mpi_mul_mpi( &Z3,  &P->Z,  &P->Z   ) ); MOD_MUL( Z3 );
+    MPI_CHK( mpi_mul_mpi( &X3,  &Z3,    &Z3     ) ); MOD_MUL( X3 );
+    MPI_CHK( mpi_mul_int( &T3,  &T3,    3       ) ); MOD_ADD( T3 );
+    MPI_CHK( mpi_mul_mpi( &X3,  &X3,    &grp->A ) ); MOD_MUL( X3 );
+    MPI_CHK( mpi_add_mpi( &T3,  &T3,    &X3     ) ); MOD_ADD( T3 );
+    MPI_CHK( mpi_mul_mpi( &X3,  &T3,    &T3     ) ); MOD_MUL( X3 );
+    MPI_CHK( mpi_sub_mpi( &X3,  &X3,    &T1     ) ); MOD_SUB( X3 );
+    MPI_CHK( mpi_sub_mpi( &X3,  &X3,    &T1     ) ); MOD_SUB( X3 );
+    MPI_CHK( mpi_sub_mpi( &T1,  &T1,    &X3     ) ); MOD_SUB( T1 );
+    MPI_CHK( mpi_mul_mpi( &T1,  &T3,    &T1     ) ); MOD_MUL( T1 );
+    MPI_CHK( mpi_mul_int( &T3,  &Y3,    8       ) ); MOD_ADD( T3 );
+    MPI_CHK( mpi_sub_mpi( &Y3,  &T1,    &T3     ) ); MOD_SUB( Y3 );
+    MPI_CHK( mpi_add_mpi( &T1,  &P->Y,  &P->Z   ) ); MOD_ADD( T1 );
+    MPI_CHK( mpi_mul_mpi( &T1,  &T1,    &T1     ) ); MOD_MUL( T1 );
+    MPI_CHK( mpi_sub_mpi( &T1,  &T1,    &T2     ) ); MOD_SUB( T1 );
+    MPI_CHK( mpi_sub_mpi( &Z3,  &T1,    &Z3     ) ); MOD_SUB( Z3 );
 
     MPI_CHK( mpi_copy( &R->X, &X3 ) );
     MPI_CHK( mpi_copy( &R->Y, &Y3 ) );
     MPI_CHK( mpi_copy( &R->Z, &Z3 ) );
 
 cleanup:
-    mpi_free( &XX ); mpi_free( &YY ); mpi_free( &YYYY ); mpi_free( &ZZ );
-    mpi_free( &t0 ); mpi_free( &t1 ); mpi_free( &t2 ); mpi_free( &t3 );
-    mpi_free( &S ); mpi_free( &t4 ); mpi_free( &t5 ); mpi_free( &t6 );
-    mpi_free( &M ); mpi_free( &t7 ); mpi_free( &t8 ); mpi_free( &T );
-    mpi_free( &X3 ); mpi_free( &t9 ); mpi_free( &t10 ); mpi_free( &t11 );
-    mpi_free( &Y3 ); mpi_free( &t12 ); mpi_free( &t13 ); mpi_free( &t14 );
-    mpi_free( &Z3 );
+    mpi_free( &T1 ); mpi_free( &T2 ); mpi_free( &T3 );
+    mpi_free( &X3 ); mpi_free( &Y3 ); mpi_free( &Z3 );
 
     return( ret );
 }