encrypt File By Private Key - Java Security

Java examples for Security:Key

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Description

encrypt File By Private Key

Demo Code


//package com.java2s;

import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;

import java.io.OutputStream;

import java.security.KeyStore;
import java.security.PrivateKey;

import javax.crypto.Cipher;

public class Main {


    public static final String KEY_STORE = "JKS";

    private static final int CACHE_SIZE = 2048;

    private static final int MAX_ENCRYPT_BLOCK = 117;

    public static byte[] encryptFileByPrivateKey(String filePath,
            String keyStorePath, String alias, String password)
            throws Exception {
        byte[] data = fileToByte(filePath);
        return encryptByPrivateKey(data, keyStorePath, alias, password);
    }//from  www  . j av  a2 s . co m

    public static void encryptFileByPrivateKey(String srcFilePath,
            String destFilePath, String keyStorePath, String alias,
            String password) throws Exception {

        PrivateKey privateKey = getPrivateKey(keyStorePath, alias, password);
        Cipher cipher = Cipher.getInstance(privateKey.getAlgorithm());
        cipher.init(Cipher.ENCRYPT_MODE, privateKey);
        File srcFile = new File(srcFilePath);
        FileInputStream in = new FileInputStream(srcFile);
        File destFile = new File(destFilePath);
        if (!destFile.getParentFile().exists()) {
            destFile.getParentFile().mkdirs();
        }
        destFile.createNewFile();
        OutputStream out = new FileOutputStream(destFile);
        byte[] data = new byte[MAX_ENCRYPT_BLOCK];
        byte[] encryptedData; // ?
        while (in.read(data) != -1) {
            encryptedData = cipher.doFinal(data);
            out.write(encryptedData, 0, encryptedData.length);
            out.flush();
        }
        out.close();
        in.close();
    }

    public static byte[] fileToByte(String filePath) throws Exception {
        byte[] data = new byte[0];
        File file = new File(filePath);
        if (file.exists()) {
            FileInputStream in = new FileInputStream(file);
            ByteArrayOutputStream out = new ByteArrayOutputStream(2048);
            byte[] cache = new byte[CACHE_SIZE];
            int nRead = 0;
            while ((nRead = in.read(cache)) != -1) {
                out.write(cache, 0, nRead);
                out.flush();
            }
            out.close();
            in.close();
            data = out.toByteArray();
        }
        return data;
    }

    public static byte[] encryptByPrivateKey(byte[] data,
            String keyStorePath, String alias, String password)
            throws Exception {

        PrivateKey privateKey = getPrivateKey(keyStorePath, alias, password);
        Cipher cipher = Cipher.getInstance(privateKey.getAlgorithm());
        cipher.init(Cipher.ENCRYPT_MODE, privateKey);
        int inputLen = data.length;
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        int offSet = 0;
        byte[] cache;
        int i = 0;

        while (inputLen - offSet > 0) {
            if (inputLen - offSet > MAX_ENCRYPT_BLOCK) {
                cache = cipher.doFinal(data, offSet, MAX_ENCRYPT_BLOCK);
            } else {
                cache = cipher.doFinal(data, offSet, inputLen - offSet);
            }
            out.write(cache, 0, cache.length);
            i++;
            offSet = i * MAX_ENCRYPT_BLOCK;
        }
        byte[] encryptedData = out.toByteArray();
        out.close();
        return encryptedData;
    }

    private static PrivateKey getPrivateKey(String keyStorePath,
            String alias, String password) throws Exception {
        KeyStore keyStore = getKeyStore(keyStorePath, password);
        PrivateKey privateKey = (PrivateKey) keyStore.getKey(alias,
                password.toCharArray());
        return privateKey;
    }

    private static KeyStore getKeyStore(String keyStorePath, String password)
            throws Exception {
        FileInputStream in = new FileInputStream(keyStorePath);
        KeyStore keyStore = KeyStore.getInstance(KEY_STORE);
        keyStore.load(in, password.toCharArray());
        in.close();
        return keyStore;
    }
}

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