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The ProximaX Sirius Chain Java SDK is a Java library for interacting with the Sirius Blockchain.

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/*
 * Copyright 2018 NEM
 *
 * 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 io.proximax.sdk.model.transaction;

import java.nio.charset.StandardCharsets;

import io.proximax.core.crypto.BlockCipher;
import io.proximax.core.crypto.CryptoEngines;
import io.proximax.core.crypto.KeyPair;
import io.proximax.core.crypto.PrivateKey;
import io.proximax.core.crypto.PublicKey;

/**
 * The secure message model defines an encoded payload.
 *
 * @since 1.0
 */
public class SecureMessage extends Message {

    /**
     * Constructor
     */
    private SecureMessage(byte[] encodedPayload, String payload) {
        super(MessageType.SECURE.getCode(), encodedPayload, payload);
    }

    public static SecureMessage createFromEncodedPayload(byte[] encodedPayload) {
        return new SecureMessage(encodedPayload, null);
    }

    public static SecureMessage create(PrivateKey senderPrivateKey, PublicKey recipientPublicKey, String payload) {
        final BlockCipher blockCipher = CryptoEngines.ed25519Engine().createBlockCipher(
                new KeyPair(senderPrivateKey), new KeyPair(recipientPublicKey));
        final byte[] encodedPayload = blockCipher.encrypt(payload.getBytes(StandardCharsets.UTF_8));
        return new SecureMessage(encodedPayload, payload);
    }

    /**
     * Decode the payload and returns it
     *
     * @param pairWithPrivateKey the key pair with private key
     * @param otherPair          the key pair of the other party
     * @return the decoded payload
     */
    public String decrypt(KeyPair pairWithPrivateKey, KeyPair otherPair) {
        if (getPayload() != null) {
            return getPayload();
        } else {
            final BlockCipher blockCipher = CryptoEngines.ed25519Engine().createBlockCipher(
                    otherPair, pairWithPrivateKey);
            final byte[] decodedPayload = blockCipher.decrypt(getEncodedPayload());

            if (decodedPayload == null) {
                throw new MessagePayloadDecodeFailureException("Failed to decode message payload");
            }
            return new String(decodedPayload, StandardCharsets.UTF_8);
        }
    }
}