Question

我正在弄乱C＃Bouncy Castle API以找到如何进行PBKDF2密钥派生。

我现在真的很无能为力。

我试过阅读Pkcs5S2ParametersGenerator.cs和PBKDF2Params.cs文件，但我真的无法弄清楚如何去做。

根据我迄今为止所做的研究，PBKDF2需要一个字符串（或char []），它是密码，盐和迭代计数。

到目前为止，迄今为止最有希望和最明显的是PBKDF2Params和Pkcs5S2ParametersGenerator。

这些似乎都没有接受字符串或char []。

有没有人用C＃做过这个或有任何线索？或者也许有人用Java实现了BouncyCastle并可以提供帮助？

提前许多：）

更新：我在Bouncy Castle找到了如何做到这一点。请看下面的答案：）

Answer 1

经过几个小时的代码处理后，我发现最简单的方法是在Pkcs5S2ParametersGenerator.cs中获取代码的一部分并创建我自己的类，当然使用其他BouncyCastle API。这与Dot Net Compact Framework（Windows Mobile）完美配合。这相当于Rfc2898DeriveBytes类，它不存在于Dot Net Compact Framework 2.0 / 3.5中。好吧，也许不是完全等同但是做的工作:)

这是PKCS5 / PKCS＃5

使用的PRF（伪随机函数）将是HMAC-SHA1

首先，首先。从http://www.bouncycastle.org/csharp/下载Bouncy Castle编译的程序集，添加BouncyCastle.Crypto.dll作为项目的参考。

之后使用下面的代码创建新的类文件。

using System;
using Org.BouncyCastle.Crypto;
using Org.BouncyCastle.Crypto.Parameters;
using Org.BouncyCastle.Crypto.Digests;
using Org.BouncyCastle.Crypto.Macs;
using Org.BouncyCastle.Math;
using Org.BouncyCastle.Security;

namespace PBKDF2_PKCS5
{
    class PBKDF2
    {

        private readonly IMac hMac = new HMac(new Sha1Digest());

        private void F(
            byte[] P,
            byte[] S,
            int c,
            byte[] iBuf,
            byte[] outBytes,
            int outOff)
        {
            byte[] state = new byte[hMac.GetMacSize()];
            ICipherParameters param = new KeyParameter(P);

            hMac.Init(param);

            if (S != null)
            {
                hMac.BlockUpdate(S, 0, S.Length);
            }

            hMac.BlockUpdate(iBuf, 0, iBuf.Length);

            hMac.DoFinal(state, 0);

            Array.Copy(state, 0, outBytes, outOff, state.Length);

            for (int count = 1; count != c; count++)
            {
                hMac.Init(param);
                hMac.BlockUpdate(state, 0, state.Length);
                hMac.DoFinal(state, 0);

                for (int j = 0; j != state.Length; j++)
                {
                    outBytes[outOff + j] ^= state[j];
                }
            }
        }

        private void IntToOctet(
            byte[] Buffer,
            int i)
        {
            Buffer[0] = (byte)((uint)i >> 24);
            Buffer[1] = (byte)((uint)i >> 16);
            Buffer[2] = (byte)((uint)i >> 8);
            Buffer[3] = (byte)i;
        }

        // Use this function to retrieve a derived key.
        // dkLen is in octets, how much bytes you want when the function to return.
        // mPassword is the password converted to bytes.
        // mSalt is the salt converted to bytes
        // mIterationCount is the how much iterations you want to perform. 


        public byte[] GenerateDerivedKey(
            int dkLen,
            byte[] mPassword,
            byte[] mSalt,
            int mIterationCount
            )
        {
            int hLen = hMac.GetMacSize();
            int l = (dkLen + hLen - 1) / hLen;
            byte[] iBuf = new byte[4];
            byte[] outBytes = new byte[l * hLen];

            for (int i = 1; i <= l; i++)
            {
                IntToOctet(iBuf, i);

                F(mPassword, mSalt, mIterationCount, iBuf, outBytes, (i - 1) * hLen);
            }

        //By this time outBytes will contain the derived key + more bytes.
       // According to the PKCS #5 v2.0: Password-Based Cryptography Standard (www.truecrypt.org/docs/pkcs5v2-0.pdf) 
       // we have to "extract the first dkLen octets to produce a derived key".

       //I am creating a byte array with the size of dkLen and then using
       //Buffer.BlockCopy to copy ONLY the dkLen amount of bytes to it
       // And finally returning it :D

        byte[] output = new byte[dkLen];

        Buffer.BlockCopy(outBytes, 0, output, 0, dkLen);

        return output;
        }


    }
}

那么如何使用这个功能呢？简单！ :) 这是一个非常简单的示例，其中密码和salt由用户提供。

private void cmdDeriveKey_Click(object sender, EventArgs e)
        {
            byte[] salt = ASCIIEncoding.UTF8.GetBytes(txtSalt.Text);

            PBKDF2 passwordDerive = new PBKDF2();


      // I want the key to be used for AES-128, thus I want the derived key to be
      // 128 bits. Thus I will be using 128/8 = 16 for dkLen (Derived Key Length) . 
      //Similarly if you wanted a 256 bit key, dkLen would be 256/8 = 32. 

            byte[] result = passwordDerive.GenerateDerivedKey(16, ASCIIEncoding.UTF8.GetBytes(txtPassword.Text), salt, 1000);

           //result would now contain the derived key. Use it for whatever cryptographic purpose now :)
           //The following code is ONLY to show the derived key in a Textbox.

            string x = "";

            for (int i = 0; i < result.Length; i++)
            {
                x += result[i].ToString("X");
            }

            txtResult.Text = x;

        }

如何检查这是否正确？有一个PBKDF2的在线JavaScript实现 http://anandam.name/pbkdf2/

我得到了一致的结果:) 如果有人得到错误的结果，请报告：）

希望这有助于某人：）

更新：确认使用此处提供的测试向量

http://tools.ietf.org/html/draft-josefsson-pbkdf2-test-vectors-00

更新：或者，对于盐，我们可以使用RNGCryptoServiceProvider。请务必引用System.Security.Cryptography命名空间。

RNGCryptoServiceProvider rng = new RNGCryptoServiceProvider();        

byte[] salt = new byte[16];

rng.GetBytes(salt);

Answer 2

我自己就遇到过这个问题，并找到了一种更直接的方法。至少在Bouncy Castle 1.7中你可以这样做（在VB中使用Org.BouncyCastle.Crypto）：

Dim bcKeyDer As New Generators.Pkcs5S2ParametersGenerator()
bcKeyDer.Init(password, salt, keyIterations)
Dim bcparam As Parameters.KeyParameter = bcKeyDer.GenerateDerivedParameters("aes256", 256)
Dim key1() As Byte = bcparam.GetKey()

我已经针对.Net的System.Security.Cryptography进行了测试，它确实有效！

Bouncy Castle C＃中的PBKDF2

2 个答案: