Java 当指数超过 10 个字节时，卡片 setExponent() 方法失败

Question

我正在尝试使用 RSA CryptoSystem 中的构建在 Java 卡上实现 modPow 功能。该代码看似微不足道，但我已发布实施。

到目前为止我的代码：

    Cipher m_encryptCipherRSA = Cipher.getInstance(Cipher.ALG_RSA_NOPAD, false); // create the cipher
    RSAPublicKey m_rsaPublicKey = (RSAPublicKey) KeyBuilder.buildKey(KeyBuilder.TYPE_RSA_PUBLIC,KeyBuilder.LENGTH_RSA_1024,false);  // create the public key
    m_random = RandomData.getInstance(RandomData.ALG_SECURE_RANDOM);
    m_random.generateData(temp1, (short)0, MODULUS_LENGTH);
    m_rsaPublicKey.setModulus(temp1,(short)0, MODULUS_LENGTH); //generate modulus
    m_random.generateData(temp1,(short)0, (short) EXPONENT_LENGTH);
    m_rsaPublicKey.setExponent(temp1,(short)0, (short)EXPONENT_LENGTH);

如果 EXPONENT_LENGTH 不超过 10 个 bytes.The Java 我的卡限制了 public 指数的维数，鳕鱼似乎工作正常。但是，我的项目基于高达 128 字节 long.Is 的数字，有没有一种方法可以根据此硬件限制创建通用 modpow 函数？有没有另一种方法可以实现仍然可行的幂指数。

Answer 1

我设法通过使用私有指数（这似乎不受 RSA 密码系统的约束）解决了这个问题。下面是工作代码。

    public byte[] modPow(byte[] x,short xOffset,short xLength,byte[] y,short yOffset,short yLength)
{
    Util.arrayCopy(y, yOffset, tempBuffer, (short)(Configuration.TEMP_OFFSET_EXPONENT+4), yLength);
    Util.arrayFillNonAtomic(tempBuffer, Configuration.TEMP_OFFSET_EXPONENT, (byte)4,(byte)0x00);
    mRsaPrivateKeyModPow.setExponent(tempBuffer,Configuration.TEMP_OFFSET_EXPONENT, (short)(yLength+4));
    mRsaCipherModPow.init(mRsaPrivateKeyModPow, Cipher.MODE_DECRYPT);
    Util.arrayCopy(x,xOffset,tempBuffer, Configuration.TEMP_OFFSET_RSA, Configuration.LENGTH_RSAOBJECT_MODULUS);
    mRsaCipherModPow.doFinal(tempBuffer,Configuration.TEMP_OFFSET_RSA, (short) (Configuration.LENGTH_RSAOBJECT_MODULUS), tempBuffer,Configuration.TEMP_OFFSET_RSA);
    mRsaPrivateKeyModPow.clearKey();
    return tempBuffer;
}

Answer 2

好吧，我尝试了 RSAPublicKey 和 RSAPrivateKey 两张不同的卡，都工作正常：

package soqPack;

import javacard.framework.*;
import javacard.security.KeyBuilder;
import javacard.security.RSAPrivateKey;
import javacard.security.RSAPublicKey;
import javacard.security.RandomData;
import javacardx.biometry.BioBuilder;
import javacardx.crypto.Cipher;

public class modPowtest extends Applet {

    //Definition Of INS in APDU command
    public static final byte INS_MOD_POW = (byte) 0x00;

    //Switch cases to choose RSA Public key or RSA Private key for ModPow()
    //P1 in APDU command.
    public static final byte USE_PUB_KEY = (byte) 0x00;
    public static final byte USE_PRI_KEY = (byte) 0x01;

    //Required objects
    byte[] tempMem;
    Cipher myCipher;
    RSAPrivateKey rsaPriKey;
    RSAPublicKey rsaPubKey;
    RandomData random;

    public static void install(byte[] bArray, short bOffset, byte bLength) {
        new modPowtest();
    }

    protected modPowtest() {
        myCipher = Cipher.getInstance(Cipher.ALG_RSA_PKCS1, false);
        rsaPriKey = (RSAPrivateKey) KeyBuilder.buildKey(KeyBuilder.TYPE_RSA_PRIVATE, KeyBuilder.LENGTH_RSA_1024, false);
        rsaPubKey = (RSAPublicKey) KeyBuilder.buildKey(KeyBuilder.TYPE_RSA_PUBLIC, KeyBuilder.LENGTH_RSA_1024, false);
        tempMem = JCSystem.makeTransientByteArray((short) 0x80, JCSystem.CLEAR_ON_DESELECT);
        random = RandomData.getInstance(RandomData.ALG_PSEUDO_RANDOM);
        register();
    }

    public void process(APDU apdu) {
        if (selectingApplet()) {
            return;
        }

        byte[] buffer = apdu.getBuffer();
        switch (buffer[ISO7816.OFFSET_INS]) {
            case INS_MOD_POW:
                modPow(apdu);
                break;
            default:
                ISOException.throwIt(ISO7816.SW_INS_NOT_SUPPORTED);
        }
    }

    public void modPow(APDU apdu) {
        byte[] buffer = apdu.getBuffer();
        switch (buffer[ISO7816.OFFSET_P1]) {
            case USE_PUB_KEY:
                random.generateData(tempMem, (short) 0x00, (short) 0x80);
                rsaPubKey.setModulus(tempMem, (short) 0x00, (short) 0x80);
                random.generateData(tempMem, (short) 0x00, (short) 0x03);
                rsaPubKey.setExponent(tempMem, (short) 0x00, (short) 0x03);
                break;
            case USE_PRI_KEY:
                random.generateData(tempMem, (short) 0x00, (short) 0x80);
                rsaPriKey.setModulus(tempMem, (short) 0x00, (short) 0x80);
                random.generateData(tempMem, (short) 0x00, (short) 0x03);
                rsaPriKey.setExponent(tempMem, (short) 0x00, (short) 0x03);
                break;
            default:
                ISOException.throwIt(ISO7816.SW_INCORRECT_P1P2);
        }

    }
}

工作如下：

Download Cap begin...
Download Cap successful.
Install Applet begin...
Install Applet successful.
Select Applet begin...
Select Applet successful.

Send: 00 00 00 00 00
Recv: 90 00

Send: 00 00 01 00 00
Recv: 90 00

更新：（与评论中的新问题和相关）：

我也在 setModulus 和 setExponent 方法之前将 tempMem[0] 的值更改为 0x69，它仍然可以正常工作。

Java 当指数超过 10 个字节时，卡片 setExponent() 方法失败

Java Card setExponent() method fails when exponent has more than 10 bytes

cryptography

rsa

exponent

javacard