如何确定Java中使用CipherOutputStream进行加密和解密所花费的时间？

Question

I try determined elapsed time for encrypt and decrypt separately in AES algorithm Is my code below true method if no please tell me where is find that?

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.security.Security;

import javax.crypto.Cipher;
import javax.crypto.CipherInputStream;
import javax.crypto.CipherOutputStream;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;

import de.flexiprovider.core.FlexiCoreProvider;

public class ExampleCrypt123 {

    public static void main(String[] args) throws Exception {
        Security.addProvider(new FlexiCoreProvider());
        Cipher cipher = Cipher.getInstance("AES128_CBC", "FlexiCore");

        KeyGenerator keyGen = KeyGenerator.getInstance("AES", "FlexiCore");
        SecretKey secKey = keyGen.generateKey();

        String cleartextFile = "F:/java_projects/cleartext.txt";
        String ciphertextFile = "F:/java_projects/ciphertextSymm.txt";
        String cleartextAgainFile = "F:/java_projects/cleartextAgainSymm.txt";

        byte[] block = new byte[16];

        FileInputStream fis = new FileInputStream(cleartextFile);
        FileOutputStream fos = new FileOutputStream(ciphertextFile);

        cipher.init(Cipher.ENCRYPT_MODE, secKey);
        // Encrypt
        long startTime = System.nanoTime();

        for(int j=0; j< 1000000; j++){
            CipherOutputStream cos = new CipherOutputStream(fos, cipher);

            int i;
            while ((i = fis.read(block)) != -1) {
                cos.write(block, 0, i);
            }
            cos.close();
        }
        long elapsedTime = System.nanoTime() - startTime;

        System.out.println("Total execution time to create 1000 objects in Java in millis: "
                + elapsedTime/1000000);

        // Decrypt



        fis = new FileInputStream(ciphertextFile);

        fos = new FileOutputStream(cleartextAgainFile);

        cipher.init(Cipher.DECRYPT_MODE, secKey);

        long startTime2 = System.nanoTime();
        for(int j=0; j< 1000000; j++){
            CipherInputStream cis = new CipherInputStream(fis, cipher);
            int i;

            while (( i = cis.read(block)) != -1) {
                fos.write(block, 0, i);
            }
            fos.close();
        }
        long elapsedTime2 = System.nanoTime() - startTime2;

        System.out.println("Total execution time to create 1000  objects in Java in millis: "
                + elapsedTime2/1000000);
    }

When run this program on my laptop give me the following results Total execution time to create 1000 objects in Java in millis: 1416 Total execution time to create 1000 objects in Java in millis: 1600

Answer 1

No, that's not right. For example you open the fis stream only once, so you actually process it only once in your encryption loop.

And you make the same mistake in your decryption loop.