diff --git a/src/option.c b/src/option.c
index 27a82fd..63c0f2e 100644
--- a/src/option.c
+++ b/src/option.c
@@ -77,7 +77,7 @@
 #if defined(FEAT_SMARTINDENT) || defined(FEAT_CINDENT)
 # define PV_CINW	OPT_BUF(BV_CINW)
 #endif
-#define PV_CM		OPT_BUF(BV_CM)
+#define PV_CM		OPT_BOTH(OPT_BUF(BV_CM))
 #ifdef FEAT_FOLDING
 # define PV_CMS		OPT_BUF(BV_CMS)
 #endif
@@ -287,9 +287,6 @@
 #if defined(FEAT_SMARTINDENT) || defined(FEAT_CINDENT)
 static char_u	*p_cinw;
 #endif
-#ifdef FEAT_CRYPT
-static long	p_cm;
-#endif
 #ifdef FEAT_COMMENTS
 static char_u	*p_com;
 #endif
@@ -866,13 +863,15 @@
 			    (char_u *)&p_cpo, PV_NONE,
 			    {(char_u *)CPO_VI, (char_u *)CPO_VIM}
 			    SCRIPTID_INIT},
-    {"cryptmethod", "cm",   P_NUM|P_VI_DEF|P_VIM,
+    {"cryptmethod", "cm",   P_STRING|P_ALLOCED|P_VI_DEF,
 #ifdef FEAT_CRYPT
 			    (char_u *)&p_cm, PV_CM,
+			    {(char_u *)"zip", (char_u *)0L}
 #else
 			    (char_u *)NULL, PV_NONE,
+			    {(char_u *)0L, (char_u *)0L}
 #endif
-			    {(char_u *)0L, (char_u *)0L} SCRIPTID_INIT},
+			    SCRIPTID_INIT},
     {"cscopepathcomp", "cspc", P_NUM|P_VI_DEF|P_VIM,
 #ifdef FEAT_CSCOPE
 			    (char_u *)&p_cspc, PV_NONE,
@@ -2915,6 +2914,9 @@
 static char *(p_bg_values[]) = {"light", "dark", NULL};
 static char *(p_nf_values[]) = {"octal", "hex", "alpha", NULL};
 static char *(p_ff_values[]) = {FF_UNIX, FF_DOS, FF_MAC, NULL};
+#ifdef FEAT_CRYPT
+static char *(p_cm_values[]) = {"zip", "blowfish", NULL};
+#endif
 #ifdef FEAT_CMDL_COMPL
 static char *(p_wop_values[]) = {"tagfile", NULL};
 #endif
@@ -5215,6 +5217,9 @@
 #if defined(FEAT_BEVAL) && defined(FEAT_EVAL)
     check_string_option(&buf->b_p_bexpr);
 #endif
+#if defined(FEAT_CRYPT)
+    check_string_option(&buf->b_p_cm);
+#endif
 #if defined(FEAT_EVAL)
     check_string_option(&buf->b_p_fex);
 #endif
@@ -5998,7 +6003,57 @@
 # endif
 	if (STRCMP(curbuf->b_p_key, oldval) != 0)
 	    /* Need to update the swapfile. */
-	    ml_set_crypt_key(curbuf, oldval, curbuf->b_p_cm);
+	    ml_set_crypt_key(curbuf, oldval, get_crypt_method(curbuf));
+    }
+
+    else if (gvarp == &p_cm)
+    {
+	if (opt_flags & OPT_LOCAL)
+	    p = curbuf->b_p_cm;
+	else
+	    p = p_cm;
+	if (check_opt_strings(p, p_cm_values, TRUE) != OK)
+	    errmsg = e_invarg;
+	else if (get_crypt_method(curbuf) > 0 && blowfish_self_test() == FAIL)
+	    errmsg = e_invarg;
+	else
+	{
+	    /* When setting the global value to empty, make it "zip". */
+	    if (*p_cm == NUL)
+	    {
+		if (new_value_alloced)
+		    free_string_option(p_cm);
+		p_cm = vim_strsave((char_u *)"zip");
+		new_value_alloced = TRUE;
+	    }
+
+	    /* Need to update the swapfile when the effective method changed.
+	     * Set "s" to the effective old value, "p" to the effective new
+	     * method and compare. */
+	    if ((opt_flags & OPT_LOCAL) && *oldval == NUL)
+		s = p_cm;  /* was previously using the global value */
+	    else
+		s = oldval;
+	    if (*curbuf->b_p_cm == NUL)
+		p = p_cm;  /* is now using the global value */
+	    else
+		p = curbuf->b_p_cm;
+	    if (STRCMP(s, p) != 0)
+		ml_set_crypt_key(curbuf, curbuf->b_p_key,
+						 crypt_method_from_string(s));
+
+	    /* If the global value changes need to update the swapfile for all
+	     * buffers using that value. */
+	    if ((opt_flags & OPT_GLOBAL) && STRCMP(p_cm, oldval) != 0)
+	    {
+		buf_T	*buf;
+
+		for (buf = firstbuf; buf != NULL; buf = buf->b_next)
+		    if (buf != curbuf && *buf->b_p_cm == NUL)
+			ml_set_crypt_key(buf, buf->b_p_key,
+					    crypt_method_from_string(oldval));
+	    }
+	}
     }
 #endif
 
@@ -8048,28 +8103,6 @@
 
 #endif
 
-#ifdef FEAT_CRYPT
-    else if (pp == &curbuf->b_p_cm)
-    {
-	if (curbuf->b_p_cm < 0)
-	{
-	    errmsg = e_positive;
-	    curbuf->b_p_cm = old_value;
-	}
-	if (curbuf->b_p_cm > 1)
-	{
-	    errmsg = e_invarg;
-	    curbuf->b_p_cm = old_value;
-	}
-	if (curbuf->b_p_cm > 0 && blowfish_self_test() == FAIL)
-	    curbuf->b_p_cm = old_value;
-
-	if (curbuf->b_p_cm != old_value && *curbuf->b_p_key != NUL)
-	    /* Need to update the swapfile. */
-	    ml_set_crypt_key(curbuf, curbuf->b_p_key, old_value);
-    }
-#endif
-
 #ifdef FEAT_WINDOWS
     /* (re)set last window status line */
     else if (pp == &p_ls)
@@ -9383,6 +9416,9 @@
 #if defined(FEAT_BEVAL) && defined(FEAT_EVAL)
 	    case PV_BEXPR: return (char_u *)&(curbuf->b_p_bexpr);
 #endif
+#if defined(FEAT_CRYPT)
+	    case PV_CM:	  return (char_u *)&(curbuf->b_p_cm);
+#endif
 #ifdef FEAT_STL_OPT
 	    case PV_STL:  return (char_u *)&(curwin->w_p_stl);
 #endif
@@ -9442,6 +9478,10 @@
 	case PV_BEXPR:	return *curbuf->b_p_bexpr != NUL
 				    ? (char_u *)&(curbuf->b_p_bexpr) : p->var;
 #endif
+#if defined(FEAT_CRYPT)
+	case PV_CM:	return *curbuf->b_p_cm != NUL
+				    ? (char_u *)&(curbuf->b_p_cm) : p->var;
+#endif
 #ifdef FEAT_STL_OPT
 	case PV_STL:	return *curwin->w_p_stl != NUL
 				    ? (char_u *)&(curwin->w_p_stl) : p->var;
@@ -9525,9 +9565,6 @@
 	case PV_CINK:	return (char_u *)&(curbuf->b_p_cink);
 	case PV_CINO:	return (char_u *)&(curbuf->b_p_cino);
 #endif
-#ifdef FEAT_CRYPT
-	case PV_CM:	return (char_u *)&(curbuf->b_p_cm);
-#endif
 #if defined(FEAT_SMARTINDENT) || defined(FEAT_CINDENT)
 	case PV_CINW:	return (char_u *)&(curbuf->b_p_cinw);
 #endif
@@ -9994,6 +10031,9 @@
 #if defined(FEAT_BEVAL) && defined(FEAT_EVAL)
 	    buf->b_p_bexpr = empty_option;
 #endif
+#if defined(FEAT_CRYPT)
+	    buf->b_p_cm = empty_option;
+#endif
 #ifdef FEAT_PERSISTENT_UNDO
 	    buf->b_p_udf = p_udf;
 #endif