问 使用密码解密大文件时内存不足异常

坏消息是: IMHO错误是由在原生 中的AES GCM-模式的错误实现造成的。即使你能让它正常工作，你也会发现一个大文件(1GB左右)的解密需要花费很多时间(也许几个小时?)。但是有一些 的好消息， ：您可以/应该使用BouncyCastle作为解密任务的服务提供者，这样解密就能工作，而且速度更快。

下面的完整示例将创建一个1GB大小的示例文件，用BouncyCastle对其进行加密，然后对其进行解密。最后，有一个文件比较显示，普通和解密的文件内容是相等的，文件将被删除。 您需要在设备上临时占用超过3GB的空闲空间才能运行此示例.

使用64 KB的缓冲区，我使用以下数据运行这个示例：

用于加密的毫秒: 14295 +解密: 16249

1 KB的缓冲区在加密方面稍微慢一点，但在解密任务上则慢得多：

用于加密的毫秒: 15250 +解密: 21952

关于您的密码的最后一句话--“AES/GCM/PKCS5Padd”在某些实现中并不存在，而且“可用”，但真正使用的算法是"AES/GCM/NoPadding“(更多细节请参见 PKCS5Padding可以采用AES/GCM模式吗？ )。

import org.bouncycastle.jce.provider.BouncyCastleProvider;
import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.spec.GCMParameterSpec;
import javax.crypto.spec.SecretKeySpec;
import java.io.*;
import java.nio.file.Files;
import java.security.*;
import java.util.Arrays;
public class GcmTestBouncyCastle {
    public static void main(String[] args) throws IOException, NoSuchPaddingException, InvalidAlgorithmParameterException,
            NoSuchAlgorithmException, IllegalBlockSizeException, BadPaddingException, NoSuchProviderException, InvalidKeyException {
        System.out.println("Encryption & Decryption with BouncyCastle AES-GCM-Mode");
        System.out.println("https://stackoverflow.com/questions/61792534/out-of-memory-exception-when-decrypt-large-file-using-cipher");
        // you need bouncy castle, get version 1.65 here:
        // https://mvnrepository.com/artifact/org.bouncycastle/bcprov-jdk15on/1.65
        Security.addProvider(new BouncyCastleProvider());
        // setup files
        // filenames
        String filenamePlain = "plain.dat";
        String filenameEncrypt = "encrypt.dat";
        String filenameDecrypt = "decrypt.dat";
        // generate a testfile of 1024 byte | 1 gb
        //createFileWithDefinedLength(filenamePlain, 1024);
        createFileWithDefinedLength(filenamePlain, 1024 * 1024 * 1024); // 1 gb
        // time measurement
        long startMilli = 0;
        long encryptionMilli = 0;
        long decryptionMilli = 0;
        // generate nonce/iv
        int GCM_NONCE_LENGTH = 12; // for a nonce of 96 bit length
        int GCM_TAG_LENGTH = 16;
        int GCM_KEY_LENGTH = 32; // 32 = 256 bit keylength, 16 = 128 bit keylength
        SecureRandom r = new SecureRandom();
        byte[] nonce = new byte[GCM_NONCE_LENGTH];
        r.nextBytes(nonce);
        // key should be generated as random byte[]
        byte[] key = new byte[GCM_KEY_LENGTH];
        r.nextBytes(key);
        // encrypt file
        startMilli = System.currentTimeMillis();
        encryptWithGcmBc(filenamePlain, filenameEncrypt, key, nonce, GCM_TAG_LENGTH);
        encryptionMilli = System.currentTimeMillis() - startMilli;
        startMilli = System.currentTimeMillis();
        decryptWithGcmBc(filenameEncrypt, filenameDecrypt, key, nonce, GCM_TAG_LENGTH);
        decryptionMilli = System.currentTimeMillis() - startMilli;
        // check that plain and decrypted files are equal
        System.out.println("SHA256-file compare " + filenamePlain + " | " + filenameDecrypt + " : "
                + Arrays.equals(sha256File(filenamePlain), sha256File(filenameDecrypt)));
        System.out.println("Milliseconds for Encryption: " + encryptionMilli + " | Decryption: " + decryptionMilli);
        // clean up with files
        Files.deleteIfExists(new File(filenamePlain).toPath());
        Files.deleteIfExists(new File(filenameEncrypt).toPath());
        Files.deleteIfExists(new File(filenameDecrypt).toPath());
    public static void encryptWithGcmBc(String filenamePlain, String filenameEnc, byte[] key, byte[] nonce, int gcm_tag_length)
            throws IOException, NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeyException,
            InvalidAlgorithmParameterException, IllegalBlockSizeException, BadPaddingException, NoSuchProviderException {
        Cipher cipher = Cipher.getInstance("AES/GCM/NoPadding", "BC");
        SecretKeySpec keySpec = new SecretKeySpec(key, "AES");
        GCMParameterSpec gcmSpec = new GCMParameterSpec(gcm_tag_length * 8, nonce);
        cipher.init(Cipher.ENCRYPT_MODE, keySpec, gcmSpec);
        try (FileInputStream fis = new FileInputStream(filenamePlain);
             BufferedInputStream in = new BufferedInputStream(fis);
             FileOutputStream out = new FileOutputStream(filenameEnc);
             BufferedOutputStream bos = new BufferedOutputStream(out)) {
            //byte[] ibuf = new byte[1024];
            byte[] ibuf = new byte[0x10000]; // = 65536
            int len;
            while ((len = in.read(ibuf)) != -1) {
                byte[] obuf = cipher.update(ibuf, 0, len);
                if (obuf != null)
                    bos.write(obuf);
            byte[] obuf = cipher.doFinal();
            if (obuf != null)
                bos.write(obuf);
    public static void decryptWithGcmBc(String filenameEnc, String filenameDec, byte[] key, byte[] nonce, int gcm_tag_length)
            throws IOException, NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeyException,
            InvalidAlgorithmParameterException, IllegalBlockSizeException, BadPaddingException, NoSuchProviderException {
        try (FileInputStream in = new FileInputStream(filenameEnc);
             FileOutputStream out = new FileOutputStream(filenameDec)) {
            //byte[] ibuf = new byte[1024];
            byte[] ibuf = new byte[0x10000]; // = 65536
            int len;
            Cipher cipher = Cipher.getInstance("AES/GCM/NoPadding", "BC");
            SecretKeySpec keySpec = new SecretKeySpec(key, "AES");
            GCMParameterSpec gcmSpec = new GCMParameterSpec(gcm_tag_length * 8, nonce);
            cipher.init(Cipher.DECRYPT_MODE, keySpec, gcmSpec);
            while ((len = in.read(ibuf)) != -1) {
                byte[] obuf = cipher.update(ibuf, 0, len);
                if (obuf != null)
                    out.write(obuf);
            byte[] obuf = cipher.doFinal();
            if (obuf != null)
                out.write(obuf);
    // just for creating a large file within seconds
    private static void createFileWithDefinedLength(String filenameString, long sizeLong) throws IOException {
        RandomAccessFile raf = new RandomAccessFile(filenameString, "rw");
        try {
            raf.setLength(sizeLong);
        } finally {
            raf.close();
    // just for file comparing
    public static byte[] sha256File(String filenameString) throws IOException, NoSuchAlgorithmException {
        byte[] buffer = new byte[8192];
        int count;
        MessageDigest md = MessageDigest.getInstance("SHA-256");
        BufferedInputStream bis = new BufferedInputStream(new FileInputStream(filenameString));
        while ((count = bis.read(buffer)) > 0) {
            md.update(buffer, 0, count);
        bis.close();
        return md.digest();
}

这似乎是实施GCM模式的一个问题。我不确定你能不能-绕开它。

如果您查看堆栈跟踪：

java.lang.OutOfMemoryError: Java heap space
    at java.util.Arrays.copyOf(Arrays.java:3236)
    at java.io.ByteArrayOutputStream.grow(ByteArrayOutputStream.java:118)
    at java.io.ByteArrayOutputStream.ensureCapacity(ByteArrayOutputStream.java:93)
    at java.io.ByteArrayOutputStream.write(ByteArrayOutputStream.java:153)
    at com.sun.crypto.provider.GaloisCounterMode.decrypt(GaloisCounterMode.java:505)

从 ByteArrayOutputStream 内部写入 GaloisCounterMode 时，内存不足的错误正在发生.您使用 FileOutputStream ，所以要么没有显示正确的代码，要么在内部使用这个 ByteArrayStream 。

如果您查看 GaloisCounterMode的来源 ，您将看到它定义了一个内部 ByteArrayOutputStream (它实际上定义了两个，但我认为这就是问题所在)：

    // buffer for storing input in decryption, not used for encryption
    private ByteArrayOutputStream ibuffer = null;

然后，稍后，它将字节写入该流。注意代码注释。

    int decrypt(byte[] in, int inOfs, int len, byte[] out, int outOfs) {
        processAAD();
        if (len > 0) {
            // store internally until decryptFinal is called because