Question

我尝试使用BouncyCastle生成公钥（因为我使用的是Unity并且无法访问ECDiffieHellmanCng），然后我将公钥传输到使用ECDiffieHellmanCng的服务器关键处理。服务器拒绝我的密钥，因为它的长度很小。与Bouncy城堡生成的公钥相比，ECDiffieHellmanCng生成的公钥大小要大得多。

有没有办法在充气城堡中生成更大的钥匙？

我尝试更改keybit大小，但收到错误消息：InvalidParameterException：未知密钥大小。

BouncyCastle生成的密钥：

3059301306072A8648CE3D020106082A8648CE3D03010703420004272F71C1D8B3DC0A7FCB1E9650EEF64EA8F639BEC97D49F8848455C2F5869F7324332D188129C84727F834EE7EE7D8EB7DFC8D40CD4ED219A4FBCEF6C15200F3

ECDiffieHellmanCng生成的密钥：

45434B35420000000055CC8665A66A7CDF2E9BF7C69A25B322C72CDBDB1EA8F348050B0A7CF32F9AAD890EA513583367977D5157B2F7FBF55661C9AE2DBAF09B1DC1EA8F193688C3C09501BEE326867ABCB41CA1029F66AF888649F0A6C0674D19670CF32461BA7B3867C1623D68829A7A9A7F1CFC6F5DB99E13C8D960AEF6F5CDAB5B3B62ED6CBEC7222C9F

以下是生成充气城堡钥匙的代码：

    const string Algorithm = "ECDH";
    const int KeyBitSize = 256;
    const int NonceBitSize = 128;
    const int MacBitSize = 128;
    const int DefaultPrimeProbability = 30;

    IAsymmetricCipherKeyPairGenerator aliceKeyGen = GeneratorUtilities.GetKeyPairGenerator(Algorithm);
    DHParametersGenerator aliceGenerator = new DHParametersGenerator();
    aliceGenerator.Init(KeyBitSize, DefaultPrimeProbability, new SecureRandom());
    DHParameters aliceParameters = aliceGenerator.GenerateParameters();
    KeyGenerationParameters aliceKGP = new DHKeyGenerationParameters(new SecureRandom(), aliceParameters);
    aliceKeyGen.Init(aliceKGP);

    AsymmetricCipherKeyPair aliceKeyPair = aliceKeyGen.GenerateKeyPair();
    IBasicAgreement aliceKeyAgree = AgreementUtilities.GetBasicAgreement(Algorithm);
    aliceKeyAgree.Init(aliceKeyPair.Private);

    SubjectPublicKeyInfo publicKeyInfo = SubjectPublicKeyInfoFactory.CreateSubjectPublicKeyInfo(aliceKeyPair.Public);
    byte[] serializedPublicBytes = publicKeyInfo.ToAsn1Object().GetDerEncoded();
    string serializedPublic = AsString(serializedPublicBytes);

public static string AsString(byte[] bytes, bool keepDashes = false)
    {
        string hex = BitConverter.ToString(bytes);
        return (keepDashes ? hex : hex.Replace("-", ""));
    }

我还试过了Mentalis.org DH库，它给了我一个更大的钥匙，但仍然只是头发太短了。

// create a new DH instance
DiffieHellman dh1 = new DiffieHellmanManaged();
// generate the public key of the first DH instance        
byte[] ke1 = dh1.CreateKeyExchange();
string publicKeyString = AsString(ke1);

来自mentalis.org库的密钥：

5F4542F9A8F5636ECCBBAC38238C97ABE757B8F65E25B181BCF41C58985E699EFD6B9606B99F7074717E83F7AC1B5E97DFF6DBA94876F74645F25F0D7FAA1528898C1BD0BB568DF15A98724093766B213769893A05B47E40410B0F395C834F68F57B2EE01852895D912C1D56675A7D8C5367B5E06DE08AAA18CBB4C69F3AE142

Answer 1

如果你是decode BouncyCastle版本，你会发现它是

30 59
SEQUENCE
  30 13
  SEQUENCE
    06 07 2A 86 48 CE 3D 02 01
    OBJECT IDENTIFIER 1.2.840.10045.2.1 (id-ecPublicKey)
    06 08 2A 86 48 CE 3D 03 01 07
    OBJECT IDENTIFIER 1.2.840.10045.3.1.7 (id-secp256r1)
  03 42 00
  BIT STRING
    04 27 2F 71 C1 D8 B3 DC 0A 7F CB 1E 96 50 EE F6
    4E A8 F6 39 BE C9 7D 49 F8 84 84 55 C2 F5 86 9F
    73 24 33 2D 18 81 29 C8 47 27 F8 34 EE 7E E7 D8
    EB 7D FC 8D 40 CD 4E D2 19 A4 FB CE F6 C1 52 00
    F3

BIT STRING的有效载荷是ecPublicKey的编码值，其曲线为secp256r1。

然后，按照SEC-1 paper的2.3.3椭圆 - 曲线 - 点 - 八位字符串转换，我们看到它被编码为

04
Uncompressed Point
  X = 27 2F 71 C1 D8 B3 DC 0A 7F CB 1E 96 50 EE F6 4E
      A8 F6 39 BE C9 7D 49 F8 84 84 55 C2 F5 86 9F 73
  Y = 24 33 2D 18 81 29 C8 47 27 F8 34 EE 7E E7 D8 EB
      7D FC 8D 40 CD 4E D2 19 A4 FB CE F6 C1 52 00 F3

遵循.NET Core import/export ECC feature的逻辑，我们看到等效的CNG blob是

// BCRYPT_ECDH_PUBLIC_P256_MAGIC (little-endian)
45 43 B4 31
// cbKey=(DWORD)32 (little-endian)
20 00 00 00
// The X bytes (big-endian):
27 2F 71 C1 D8 B3 DC 0A 7F CB 1E 96 50 EE F6 4E
A8 F6 39 BE C9 7D 49 F8 84 84 55 C2 F5 86 9F 73
// The Y bytes (big-endian):
27 2F 71 C1 D8 B3 DC 0A 7F CB 1E 96 50 EE F6 4E
A8 F6 39 BE C9 7D 49 F8 84 84 55 C2 F5 86 9F 73

为什么BouncyCastle生成的密钥小于.Net的ECDiffieHellmanCng

1 个答案: