decrypt By Private Key - Java Security

Java examples for Security:Key

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Description

decrypt By Private Key

Demo Code


//package com.java2s;

import java.io.ByteArrayOutputStream;

import java.io.FileInputStream;

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 MAX_DECRYPT_BLOCK = 128;

    public static byte[] decryptByPrivateKey(byte[] encryptedData,
            String keyStorePath, String alias, String password)
            throws Exception {

        PrivateKey privateKey = getPrivateKey(keyStorePath, alias, password);
        Cipher cipher = Cipher.getInstance(privateKey.getAlgorithm());
        cipher.init(Cipher.DECRYPT_MODE, privateKey);

        int inputLen = encryptedData.length;
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        int offSet = 0;
        byte[] cache;
        int i = 0;

        while (inputLen - offSet > 0) {
            if (inputLen - offSet > MAX_DECRYPT_BLOCK) {
                cache = cipher.doFinal(encryptedData, offSet,
                        MAX_DECRYPT_BLOCK);
            } else {
                cache = cipher.doFinal(encryptedData, offSet, inputLen
                        - offSet);//from   w  w w .j ava2  s. c  o  m
            }
            out.write(cache, 0, cache.length);
            i++;
            offSet = i * MAX_DECRYPT_BLOCK;
        }
        byte[] decryptedData = out.toByteArray();
        out.close();
        return decryptedData;
    }

    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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