jvz commented on a change in pull request #177: URL: https://github.com/apache/mina-sshd/pull/177#discussion_r633122293
########## File path: sshd-core/src/main/java/org/apache/sshd/common/kex/MontgomeryCurve.java ########## @@ -0,0 +1,158 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one + * or more contributor license agreements. See the NOTICE file + * distributed with this work for additional information + * regarding copyright ownership. The ASF licenses this file + * to you under the Apache License, Version 2.0 (the + * "License"); you may not use this file except in compliance + * with the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, + * software distributed under the License is distributed on an + * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY + * KIND, either express or implied. See the License for the + * specific language governing permissions and limitations + * under the License. + */ + +package org.apache.sshd.common.kex; + +import java.io.IOException; +import java.io.StreamCorruptedException; +import java.io.UncheckedIOException; +import java.security.GeneralSecurityException; +import java.security.InvalidKeyException; +import java.security.KeyFactory; +import java.security.KeyPair; +import java.security.KeyPairGenerator; +import java.security.PublicKey; +import java.security.spec.InvalidKeySpecException; +import java.security.spec.X509EncodedKeySpec; + +import javax.crypto.KeyAgreement; + +import org.apache.sshd.common.OptionalFeature; +import org.apache.sshd.common.digest.BuiltinDigests; +import org.apache.sshd.common.digest.Digest; +import org.apache.sshd.common.digest.DigestFactory; +import org.apache.sshd.common.keyprovider.KeySizeIndicator; +import org.apache.sshd.common.util.io.der.ASN1Object; +import org.apache.sshd.common.util.io.der.DERParser; +import org.apache.sshd.common.util.security.SecurityUtils; + +/** + * Provides implementation details for Montgomery curves and their key exchange algorithms Curve25519/X25519 and + * Curve448/X448 specified in RFC 7748 and RFC 8731. Montgomery curves provide improved security and flexibility over + * Weierstrass curves used in ECDH. + * + * @see <a href="https://www.rfc-editor.org/info/rfc7748";>RFC 7748</a> + * @see <a href="https://www.rfc-editor.org/info/rfc8731";>RFC 8731</a> + */ +public enum MontgomeryCurve implements KeySizeIndicator, OptionalFeature { + + /** + * X25519 uses Curve25519 and SHA-256 with a 32-byte key size. + */ + x25519("X25519", 32, BuiltinDigests.sha256, + new byte[] { 0x30, 0x2a, 0x30, 0x05, 0x06, 0x03, 0x2b, 0x65, 0x6e, 0x03, 0x21, 0x00 }), Review comment: While I originally considered this idea to be a bit hacky, I've since seen it in more than one other XDH implementation for Java. The X.509 encoded form of an X25519 or X448 key are always going to have the same prefix data (the algorithm id and key length in some ASN.1 format). Thus, we can portably use the `X509EncodedKeySpec` class to serialize and deserialize XDH public keys without needing a full ASN.1/DER encoding library like in BouncyCastle. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
