如何将十六进制公钥转换为 ASN.1 主题公共密钥信息结构，用于迪菲-赫尔曼密钥交换？

Question

我正在尝试实现迪菲-赫尔曼密钥交换，以使用JAVA加密包生成用于加密/解密的对称密钥。这需要双方之间的公钥交换。客户端共享的公钥是 1024 位十六进制字符串，应用于计算共享密钥。如何将此字符串转换为编码的密钥格式（ASN.1 主题公钥信息结构）以创建公钥对象。考虑一个示例公钥字符串。参数 p 和 g 被馈送到输入DH参数规格对象中。示例实现：自动生成密钥对：    KeyPairGenerator clientKpairGen = keyPairGenerator.getInstance("DiffieHellman");    clientKpairGen.initialize(inputDHParameterSpec);    KeyPair clientKpair = clientKpairGen.generateKeyPair();    byte[] clientPubKeyEnc = clientKpair.getPublic().getEncoded();    X509EncodedKeySpec testPubKeySpec = new X509EncodedKeySpec(clientPubKeyEnc);    KeyFactory keyFactory = KeyFactory.getInstance("DiffieHellman");    PublicKey clientPubKey = keyFactory.generatePublic(testPubKeySpec);十六进制公钥 - 失败：    String testPublicKey = "85f04dd00345642ad12b65bd1a7c38728bff0b8e281ddb6ac4f2739e82a02145daabf23d173c933913b1f844059710e9125591569de427eae1d269accbfa3305069deb7622d1da3ad9820d11bd24fdcce5381d2df99bda314394738dfcbe210eae247b1303e79297ff746cd919e189f6a5776e6ecc24c8900de0f38f159072de";    X509EncodedKeySpec testPubKeySpec = new X509EncodedKeySpec(hexStringToByteArray(testPublicKey));    KeyFactory keyFactory = KeyFactory.getInstance("DiffieHellman");    PublicKey clientPubKey = keyFactory.generatePublic(testPubKeySpec);//Failing here在第一个代码块中创建的byte[] 具有 ASN.1 编码格式的公钥，但十六进制字符串到字节数组（testPublicKey）仅将十六进制转换为字节 []。因此，在标记的行上获得以下错误。Exception in thread "main" java.security.spec.InvalidKeySpecException: Inappropriate key specification    at com.sun.crypto.provider.DHKeyFactory.engineGeneratePublic(DHKeyFactory.java:85)    at java.security.KeyFactory.generatePublic(KeyFactory.java:334)    at MWK_DHGen.main(MWK_DHGen.java:87)Caused by: java.security.InvalidKeyException: Error parsing key encoding    at com.sun.crypto.provider.DHPublicKey.<init>(DHPublicKey.java:178)    at com.sun.crypto.provider.DHKeyFactory.engineGeneratePublic(DHKeyFactory.java:78)    ... 2 more有人可以帮助如何将这个十六进制转换为这里所要求的格式吗？还鼓励使用此十六进制字符串来获取密钥的不同实现。

Answer 1

如果您已经拥有域参数（p，g）并且只有公钥的整数值，那么DHP公共密钥规格而不是a是要走的路：X509EncodedKeySpec

String testPublicKey = "85f04dd00345642ad12b65bd1a7c38728bff0b8e281ddb6ac4f2739e82a02145daabf23d173c933913b1f844059710e9125591569de427eae1d269accbfa3305069deb7622d1da3ad9820d11bd24fdcce5381d2df99bda314394738dfcbe210eae247b1303e79297ff746cd919e189f6a5776e6ecc24c8900de0f38f159072de";

BigInteger publicKeyInteger = new BigInteger(testPublicKey, 16);

KeyFactory keyFactory = KeyFactory.getInstance("DiffieHellman");

PublicKey clientPubKey = keyFactory.generatePublic(new DHPublicKeySpec(publicKeyInteger, g, p));