4

我正在尝试在 Android 中使用 SpongyCastle 生成 ECDSA 密钥对。这是代码：

static {
    Security.insertProviderAt(new org.spongycastle.jce.provider.BouncyCastleProvider(), 1);
}

public static KeyPair generate() {
        ECParameterSpec ecSpec = ECNamedCurveTable.getParameterSpec("prime256v1");
        KeyPairGenerator generator = KeyPairGenerator.getInstance("ECDSA", "SC");
        generator.initialize(ecSpec, new SecureRandom());
        KeyPair keyPair = g.generateKeyPair();
        Log.i(TAG, "EC Pub Key generated: " + utils.bytesToHex(keyPair.getPublic().getEncoded()));
        Log.i(TAG, "EC Private Key generated: " + utils.bytesToHex(keyPair.getPrivate().getEncoded()));            
       return generator.generateKeyPair();
}

出了点问题，因为我总是得到类似公钥的例子：

3059301306072A8648CE3D020106082A8648CE3D03010703420004483ABA9F322240010ECF00E818C041A60FE71A2BD64C64CD5A60519985F110AEDE6308027D2730303F5E2478F083C7F5BB683DCAC22BFEB62F3A48BD01009F40

和私钥：

308193020100301306072A8648CE3D020106082A8648CE3D030107047930770201010420219AB4B3701630973A4B2917D53F69A4BE6DAD61F48016BFEF147B2999575CB2A00A06082A8648CE3D030107A14403420004483ABA9F322240010ECF00E818C041A60FE71A2BD64C64CD5A60519985F110AEDE6308027D2730303F5E2478F083C7F5BB683DCAC22BFEB62F3A48BD01009F40

站点ECDSA 示例给了我“无效的 ECDSA 签名消息”，它们似乎与较小的私钥非常不同，并且总是以在同一站点中生成的“04”公钥开头。

此外，我的后端验证给了我错误“无效点编码 0x30”

后端 Java 方法检查是：

public ECPublicKey getPublicKeyFromHex(String publicKeyHex)
        throws NoSuchAlgorithmException, DecoderException, ApplicationGenericException {
    byte[] rawPublicKey = Hex.decodeHex(publicKeyHex.toCharArray());
    ECPublicKey ecPublicKey = null;
    KeyFactory kf = null;

    ECNamedCurveParameterSpec ecNamedCurveParameterSpec = ECNamedCurveTable.getParameterSpec("prime256v1");
    ECCurve curve = ecNamedCurveParameterSpec.getCurve();
    EllipticCurve ellipticCurve = EC5Util.convertCurve(curve, ecNamedCurveParameterSpec.getSeed());
    java.security.spec.ECPoint ecPoint = ECPointUtil.decodePoint(ellipticCurve, rawPublicKey);
    java.security.spec.ECParameterSpec ecParameterSpec = EC5Util.convertSpec(ellipticCurve,
            ecNamedCurveParameterSpec);
    java.security.spec.ECPublicKeySpec publicKeySpec = new java.security.spec.ECPublicKeySpec(ecPoint,
            ecParameterSpec);

    kf = KeyFactory.getInstance("ECDSA", new BouncyCastleProvider());

    try {
        ecPublicKey = (ECPublicKey) kf.generatePublic(publicKeySpec);
    } catch (Exception e) {
        throw new ApplicationGenericException(e.getMessage(), e.getCause());
    }

    return ecPublicKey;
}
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2 回答 2

7

PublicKeyJava 对 a的默认编码"X.509"不仅仅是 EC 点；它是一个 ASN.1 结构，标识算法（EC）和参数（这里是 prime256v1）加上一个 BIT STRING 包裹点；参见rfc5280 第 4.2.1.7 节和rfc3279 第 2.3.5 节。

类似地，默认编码PrivateKey是"PKCS#8"（未加密），它是一个包含 AlgorithmIdentifier 加上 OCTET STRING 包装数据的结构，在这种情况下包含私钥值和公钥副本，请参阅rfc5208 第 5 节和 C.4在http://www.secg.org上记录 SEC 1，其中[0]省略了标签但[1]存在标签。

要将它们（其中一个或两个）读回Java，请分别获取 aKeyFactory.getInstance("EC")并generate{Public,Private}在X509EncodedKeySpecor上使用PKCS8EncodedKeySpec。ECDSA 和 ECDH（以及 ECMQV 等）使用相同的密钥结构，这与使用相同数学结构 ($Z_p^*$) 但表示略有不同的经典整数 DSA 和 DH 不同。

PS：javadoc forjava.security.Key告诉你大部分内容。

于 2016-10-20T03:36:59.087 回答
2

更实际的例子。将生成的公钥转换为解码的字节数组或十六进制字符串： 

public String getPublicKeyAsHex(PublicKey publicKey){

    ECPublicKey ecPublicKey = (ECPublicKey)publicKey;
    ECPoint ecPoint = ecPublicKey.getW();

    byte[] publicKeyBytes = new byte[PUBLIC_KEY_LENGTH];
    writeToStream(publicKeyBytes, 0, ecPoint.getAffineX(), PRIVATE_KEY_LENGTH);
    writeToStream(publicKeyBytes, PRIVATE_KEY_LENGTH, ecPoint.getAffineY(), PRIVATE_KEY_LENGTH);

    String hex = Hex.toHexString(publicKeyBytes);

    logger.debug("Public key bytes: " + Arrays.toString(publicKeyBytes));
    logger.debug("Public key hex: " + hex);

    return hex;
}

private void writeToStream(byte[] stream, int start, BigInteger value, int size) {
    byte[] data = value.toByteArray();
    int length = Math.min(size, data.length);
    int writeStart = start + size - length;
    int readStart = data.length - length;
    System.arraycopy(data, readStart, stream, writeStart, length);
}

将解码的字节数组转换回PublicKey：

KeyFactory factory = KeyFactory.getInstance(ALGORITHM, ALGORITHM_PROVIDER);

ECNamedCurveParameterSpec spec = ECNamedCurveTable.getParameterSpec(CURVE);

ECNamedCurveSpec params = new ECNamedCurveSpec(CURVE, spec.getCurve(), spec.getG(), spec.getN());

BigInteger xCoordinate = new BigInteger(1, Arrays.copyOfRange(decodedPublicKey, 0, PRIVATE_KEY_LENGTH));
BigInteger yCoordinate = new BigInteger(1, Arrays.copyOfRange(decodedPublicKey, PRIVATE_KEY_LENGTH, PUBLIC_KEY_LENGTH));
java.security.spec.ECPoint w = new java.security.spec.ECPoint(xCoordinate, yCoordinate);

PublicKey encodedPublicKey = factory.generatePublic(new java.security.spec.ECPublicKeySpec(w, params));
于 2016-10-24T08:07:29.363 回答