Main.java Source code

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Here is the source code for Main.java

Source

//package com.java2s;
/**
 * Copyright 2016 kubotaku1119 <kubotaku1119@gmail.com>
 * <p/>
 * 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
 * <p/>
 * http://www.apache.org/licenses/LICENSE-2.0
 * <p/>
 * 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.
 */

import android.annotation.TargetApi;

import android.content.Context;

import android.os.Build;

import android.security.KeyPairGeneratorSpec;
import android.security.keystore.KeyGenParameterSpec;
import android.security.keystore.KeyProperties;

import android.util.Base64;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.math.BigInteger;
import java.security.InvalidAlgorithmParameterException;
import java.security.KeyPairGenerator;
import java.security.KeyStore;
import java.security.KeyStoreException;
import java.security.NoSuchAlgorithmException;
import java.security.NoSuchProviderException;
import java.security.PrivateKey;

import java.security.cert.CertificateException;
import java.util.Calendar;
import java.util.Date;
import javax.crypto.Cipher;
import javax.crypto.CipherInputStream;

import javax.security.auth.x500.X500Principal;

public class Main {
    private static final String KEY_PROVIDER = "AndroidKeyStore";
    private static final String KEY_ALIAS = "otegaru_iot";
    private static final String ALGORITHM_OLD = "RSA/ECB/PKCS1Padding";
    private static final String ALGORITHM = "RSA/ECB/OAEPWithSHA-256AndMGF1Padding";

    @TargetApi(Build.VERSION_CODES.JELLY_BEAN_MR2)
    private static String decryptStringImpl(Context context, final String encryptedText) {
        String plainText = null;
        try {
            final KeyStore keyStore = getKeyStore(context);

            PrivateKey privateKey = (PrivateKey) keyStore.getKey(KEY_ALIAS, null);

            String algorithm = ALGORITHM_OLD;
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
                algorithm = ALGORITHM;
            }
            Cipher cipher = Cipher.getInstance(algorithm);
            cipher.init(Cipher.DECRYPT_MODE, privateKey);

            CipherInputStream cipherInputStream = new CipherInputStream(
                    new ByteArrayInputStream(Base64.decode(encryptedText, Base64.DEFAULT)), cipher);

            ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
            int b;
            while ((b = cipherInputStream.read()) != -1) {
                outputStream.write(b);
            }
            outputStream.close();
            plainText = outputStream.toString("UTF-8");
        } catch (Exception e) {
            e.printStackTrace();
        }
        return plainText;
    }

    @TargetApi(Build.VERSION_CODES.JELLY_BEAN_MR2)
    private static KeyStore getKeyStore(Context context) {
        KeyStore keyStore = null;
        try {
            keyStore = KeyStore.getInstance(KEY_PROVIDER);
            keyStore.load(null);

            if (!keyStore.containsAlias(KEY_ALIAS)) {
                if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
                    // for api level 23+
                    generateNewKey();
                } else {
                    // for api level 18 - 22
                    generateNewKeyOld(context);
                }
            }

        } catch (KeyStoreException e) {
            e.printStackTrace();
        } catch (CertificateException e) {
            e.printStackTrace();
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

        return keyStore;
    }

    @TargetApi(Build.VERSION_CODES.M)
    private static void generateNewKey() {
        try {
            KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance(KeyProperties.KEY_ALGORITHM_RSA,
                    KEY_PROVIDER);

            keyPairGenerator.initialize(new KeyGenParameterSpec.Builder(KEY_ALIAS, KeyProperties.PURPOSE_DECRYPT)
                    .setDigests(KeyProperties.DIGEST_SHA256, KeyProperties.DIGEST_SHA512)
                    .setEncryptionPaddings(KeyProperties.ENCRYPTION_PADDING_RSA_OAEP).build());
            keyPairGenerator.generateKeyPair();

        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
        } catch (NoSuchProviderException e) {
            e.printStackTrace();
        } catch (InvalidAlgorithmParameterException e) {
            e.printStackTrace();
        }
    }

    @TargetApi(Build.VERSION_CODES.JELLY_BEAN_MR2)
    private static void generateNewKeyOld(Context context) {
        try {
            KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance(KeyProperties.KEY_ALGORITHM_RSA,
                    KEY_PROVIDER);

            Calendar instance = Calendar.getInstance();
            Date start = instance.getTime();

            instance.add(Calendar.YEAR, 1);
            Date end = instance.getTime();

            keyPairGenerator.initialize(new KeyPairGeneratorSpec.Builder(context).setAlias(KEY_ALIAS)
                    .setSubject(new X500Principal("CN=" + KEY_ALIAS)).setSerialNumber(BigInteger.valueOf(20151021))
                    .setStartDate(start).setEndDate(end).build());

            keyPairGenerator.generateKeyPair();

        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
        } catch (NoSuchProviderException e) {
            e.printStackTrace();
        } catch (InvalidAlgorithmParameterException e) {
            e.printStackTrace();
        }
    }
}