如何用Java对大数据进行RSA加解密

Question

我正在尝试使用 RSA 和 OAEPPadding 对实际较大的数据（例如 10 KB）执行非对称加密和解密。

许多 Stackoverflow 文章提到使用混合方法 [不对称 + 对称]，但我并不是在寻找这种方法。我故意要求非对称加密。

我初始化了加密和解密密码，如下所示：

mDecryptCipher = Cipher.getInstance("RSA/None/OAEPPadding", new BouncyCastleProvider());
mDecryptCipher.init(Cipher.DECRYPT_MODE, mPrivateKey);
Log.d(TAG, "Decrypt Cipher is successfully created");

mEncryptCipher = Cipher.getInstance("RSA/None/OAEPPadding", new BouncyCastleProvider());
mEncryptCipher.init(Cipher.ENCRYPT_MODE, mPublicKey);
Log.d(TAG, "Encrypt Cipher is successfully created");

以下是我尝试加密或解密大小为 10 KB 的大数据的代码。

// Encrypt
byte[] encryptedPayload = mEncryptCipher.doFinal(payload);

// Decrypt
byte[] decryptedPayload = mDecryptCipher.doFinal(payload);

以下是我收到的异常：

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: too much data for RSA block
    at org.bouncycastle.jcajce.provider.asymmetric.rsa.CipherSpi.engineDoFinal(Unknown Source)
    at java.base/javax.crypto.Cipher.doFinal(Cipher.java:2205)

请让我知道如何对大数据执行 RSA 加密和解密。

Answer 1

Java Cipher 对象允许我们检索块大小，并使用它来执行重复的加密和解密，这将使我们克服“RSA 块数据太多”例外。

以下是加密的逻辑：

public byte[] encrypt(String data) {
    Log.d(TAG, "Encryption begins");
    byte[] payload = data.getBytes(StandardCharsets.UTF_8);
    int payloadLength = payload.length;
    int blockSize = mEncryptCipher.getBlockSize();
    Log.d(TAG, "blockSize: " + blockSize + "; payloadLength: " + payloadLength);

    ByteArrayOutputStream stream = new ByteArrayOutputStream();
    int start = 0, end = 0;
    while (end < payloadLength) {
        end = end + blockSize;
        if (end > payloadLength) {
            end = payloadLength;
        }
        Log.d(TAG, "start: " + start + "; end: " + end + "; block: " + (end - start));
        try {
            byte[] encryptedSlice = mEncryptCipher.doFinal(payload, start, (end - start));
            Log.d(TAG, "Encrypted Slice Length: " + encryptedSlice.length);
            stream.write(encryptedSlice);
            start = end;
        } catch (IOException | BadPaddingException | IllegalBlockSizeException e) {
            Log.e(TAG, "update failed");
            e.printStackTrace();
            break;
        }
    }
    byte[] encryptedPayload = stream.toByteArray();
    try {
        stream.close();
    } catch (IOException e) {
        e.printStackTrace();
    }
    Log.d(TAG, "encryptedPayload length: " + encryptedPayload.length);
    byte[] base64EncryptedPayload = org.apache.commons.codec.binary.Base64.encodeBase64(encryptedPayload);
    Log.d(TAG, "base64EncryptedPayload length: " + base64EncryptedPayload.length);
    Log.d(TAG, "Encryption ends");
    return base64EncryptedPayload;
}

以下是解密的逻辑：

public String decrypt(byte[] base64EncodedData) {
    Log.d(TAG, "Decryption begins");
    Log.d(TAG, "base64EncodedData length: " + base64EncodedData.length);
    byte[] encryptedData = org.apache.commons.codec.binary.Base64.decodeBase64(base64EncodedData);
    Log.d(TAG, "encryptedData length: " + encryptedData.length);

    ByteArrayOutputStream stream = new ByteArrayOutputStream();
    int payloadLength = encryptedData.length;
    int blockSize = mDecryptCipher.getBlockSize();
    int start = 0, end = 0;
    while (start < payloadLength) {
        end = end + blockSize;
        if (end > payloadLength) {
            end = payloadLength;
        }

        Log.d(TAG, "start: " + start + "; end: " + end + "; block: " + (end - start));
        try {
            byte[] decryptedBlockData = mDecryptCipher.doFinal(encryptedData, start, (end - start));
            Log.d(TAG, "decryptedBlockData Length: " + decryptedBlockData.length);
            stream.write(decryptedBlockData);
            start = end;
        } catch (BadPaddingException | IllegalBlockSizeException | IOException e) {
            Log.e(TAG, "Slicing failed");
            e.printStackTrace();
            break;
        }
    }
    String payload = stream.toString();
    try {
        stream.close();
    } catch (IOException e) {
        e.printStackTrace();
    }
    Log.d(TAG, "Decryption ends");
    return payload;
}

请注意，在我的例子中，以下是 Cipher 对象的详细信息：

EncryptCipher:

getBlockSize: 470
getAlgorithm: RSA/None/OAEPPadding
getProvider Name: BC
getProvider Info: BouncyCastle Security Provider v1.70

DecryptCipher:

getBlockSize: 512
getAlgorithm: RSA/None/OAEPPadding
getProvider Name: BC
getProvider Info: BouncyCastle Security Provider v1.70

我是开放的以及任何更好的解决方案。