| /* |
| * 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.tuweni.devp2p.v5.encrypt |
| |
| import org.apache.tuweni.bytes.Bytes |
| import org.apache.tuweni.devp2p.v5.misc.SessionKey |
| import org.bouncycastle.crypto.digests.SHA256Digest |
| import org.bouncycastle.crypto.generators.HKDFBytesGenerator |
| import org.bouncycastle.crypto.params.HKDFParameters |
| |
| /** |
| * Generates session keys on handshake, using HKDF key derivation function |
| */ |
| object SessionKeyGenerator { |
| |
| const val DERIVED_KEY_SIZE: Int = 16 |
| |
| private val INFO_PREFIX = Bytes.wrap("discovery v5 key agreement".toByteArray()) |
| |
| /** |
| * Executes session keys generation |
| * |
| * @param srcNodeId sender node identifier |
| * @param destNodeId receiver node identifier |
| * @param secret the input keying material or seed |
| * @param idNonce nonce used as salt |
| */ |
| fun generate(srcNodeId: Bytes, destNodeId: Bytes, secret: Bytes, idNonce: Bytes): SessionKey { |
| val info = Bytes.wrap(INFO_PREFIX, srcNodeId, destNodeId) |
| |
| val hkdf = HKDFBytesGenerator(SHA256Digest()) |
| val params = HKDFParameters(secret.toArray(), idNonce.toArray(), info.toArray()) |
| hkdf.init(params) |
| return SessionKey(derive(hkdf), derive(hkdf), derive(hkdf)) |
| } |
| |
| private fun derive(hkdf: HKDFBytesGenerator): Bytes { |
| val result = ByteArray(DERIVED_KEY_SIZE) |
| hkdf.generateBytes(result, 0, result.size) |
| return Bytes.wrap(result) |
| } |
| } |