-.\" $OpenBSD: EC_GROUP_copy.3,v 1.11 2021/09/11 17:59:04 schwarze Exp $
-.\" full merge up to: OpenSSL aafbe1cc Jun 12 23:42:08 2013 +0100
+.\" $OpenBSD: EC_GROUP_copy.3,v 1.12 2021/09/14 13:47:59 schwarze Exp $
+.\" full merge up to: OpenSSL d900a015 Oct 8 14:40:42 2015 +0200
.\" selective merge up to: OpenSSL 24c23e1f Aug 22 10:51:25 2019 +0530
.\"
-.\" This file was written by Matt Caswell <matt@openssl.org>
+.\" This file was written by Matt Caswell <matt@openssl.org>,
+.\" Dr. Stephen Henson <steve@openssl.org>,
.\" and Jayaram X Matta <jayaramx.matta@intel.com>.
.\" Copyright (c) 2013, 2015, 2019 The OpenSSL Project. All rights reserved.
.\"
.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
.\" OF THE POSSIBILITY OF SUCH DAMAGE.
.\"
-.Dd $Mdocdate: September 11 2021 $
+.Dd $Mdocdate: September 14 2021 $
.Dt EC_GROUP_COPY 3
.Os
.Sh NAME
will return
.Dv NID_undef .
.Pp
-The asn1_flag value on a curve is used to determine whether there is a
-specific ASN.1 OID to describe the curve or not.
-If the asn1_flag is 1 then this is a named curve with an associated ASN.1 OID.
-If not then asn1_flag is 0.
+The asn1_flag value is used to determine whether the curve encoding
+uses explicit parameters or a named curve using an ASN.1 OID:
+many applications only support the latter form.
+If asn1_flag is the default value
+.Dv OPENSSL_EC_NAMED_CURVE ,
+then the named curve form is used and the parameters must have a
+corresponding named curve NID set.
+If asn1_flags is
+.Dv OPENSSL_EC_EXPLICIT_CURVE ,
+the parameters are explicitly encoded.
The functions
.Fn EC_GROUP_get_asn1_flag
and
.Fn EC_GROUP_set_asn1_flag
get and set the status of the asn1_flag for the curve.
-If set, then the curve_name must also be set.
.Pp
The point_conversion_form for a curve controls how
.Vt EC_POINT