8166597: Crypto support for the EdDSA Signature Algorithm

Reviewed-by: weijun, mullan, wetmore

src/java.base/share/classes/java/security/interfaces/EdECPrivateKey.java

@@ -0,0 +1,55 @@
+/*
+ * Copyright (c) 2020, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+package java.security.interfaces;
+
+import java.security.PrivateKey;
+import java.util.Optional;
+
+/**
+ * An interface for an elliptic curve private key as defined by
+ * <a href="https://tools.ietf.org/html/rfc8032">RFC 8032: Edwards-Curve
+ * Digital Signature Algorithm (EdDSA)</a>. These keys are distinct from the
+ * keys represented by {@code ECPrivateKey}, and they are intended for use
+ * with algorithms based on RFC 8032 such as the EdDSA {@code Signature}
+ * algorithm.
+ * <p>
+ * An Edwards-Curve private key is a bit string. This interface only supports bit
+ * string lengths that are a multiple of 8, and the key is represented using
+ * a byte array.
+ *
+ * @since 15
+ */
+public interface EdECPrivateKey extends EdECKey, PrivateKey {
+
+    /**
+     * Get a copy of the byte array representing the private key. This method
+     * may return an empty {@code Optional} if the implementation is not
+     * willing to produce the private key value.
+     *
+     * @return an {@code Optional} containing the private key byte array.
+     * If the key is not available, then an empty {@code Optional}.
+     */
+    Optional<byte[]> getBytes();
+}