| // Copyright 2017 Google Inc. |
| // |
| // Licensed 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 com.google.crypto.tink.subtle; |
| |
| import com.google.crypto.tink.util.Bytes; |
| import java.security.GeneralSecurityException; |
| import java.security.KeyPair; |
| import java.security.interfaces.ECPrivateKey; |
| import java.security.interfaces.ECPublicKey; |
| |
| /** |
| * HKDF-based ECIES-KEM (key encapsulation mechanism) for ECIES sender. |
| * |
| * @since 1.0.0 |
| */ |
| public final class EciesHkdfSenderKem { |
| private final ECPublicKey recipientPublicKey; |
| |
| /** A container for key parts generated by the KEM. */ |
| public static final class KemKey { |
| private final Bytes kemBytes; |
| private final Bytes symmetricKey; |
| |
| public KemKey(final byte[] kemBytes, final byte[] symmetricKey) { |
| if (kemBytes == null) { |
| throw new NullPointerException("KemBytes must be non-null"); |
| } |
| if (symmetricKey == null) { |
| throw new NullPointerException("symmetricKey must be non-null"); |
| } |
| this.kemBytes = Bytes.copyFrom(kemBytes); |
| this.symmetricKey = Bytes.copyFrom(symmetricKey); |
| } |
| |
| public byte[] getKemBytes() { |
| return kemBytes.toByteArray(); |
| } |
| |
| public byte[] getSymmetricKey() { |
| return symmetricKey.toByteArray(); |
| } |
| } |
| |
| public EciesHkdfSenderKem(final ECPublicKey recipientPublicKey) { |
| this.recipientPublicKey = recipientPublicKey; |
| } |
| |
| public KemKey generateKey( |
| String hmacAlgo, |
| final byte[] hkdfSalt, |
| final byte[] hkdfInfo, |
| int keySizeInBytes, |
| EllipticCurves.PointFormatType pointFormat) |
| throws GeneralSecurityException { |
| KeyPair ephemeralKeyPair = EllipticCurves.generateKeyPair(recipientPublicKey.getParams()); |
| ECPublicKey ephemeralPublicKey = (ECPublicKey) ephemeralKeyPair.getPublic(); |
| ECPrivateKey ephemeralPrivateKey = (ECPrivateKey) ephemeralKeyPair.getPrivate(); |
| byte[] sharedSecret = EllipticCurves.computeSharedSecret( |
| ephemeralPrivateKey, recipientPublicKey); |
| byte[] kemBytes = |
| EllipticCurves.pointEncode( |
| ephemeralPublicKey.getParams().getCurve(), pointFormat, ephemeralPublicKey.getW()); |
| byte[] symmetricKey = |
| Hkdf.computeEciesHkdfSymmetricKey( |
| kemBytes, sharedSecret, hmacAlgo, hkdfSalt, hkdfInfo, keySizeInBytes); |
| return new KemKey(kemBytes, symmetricKey); |
| } |
| } |