Bouncy Castle C#中的PBKDF2

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.

我尝试通过Pkcs5S2ParametersGenerator.cs和PBKDF2Params.cs文件阅读,但我真的无法弄清楚如何做到这一点.

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,迄今为止最有前途和最明显的是PBKDF2Params和Pkcs5S2ParametersGenerator.

这些似乎都不接受字符串或char [].

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

Thanx提前很多:)

更新:我在Bouncy Castle找到了如何做到这一点.看下面的答案:)

Answer 1

经过几个小时的代码后,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,第一件事.从http://www.bouncycastle.org/csharp/下载Bouncy Castle编译程序集,将其添加BouncyCastle.Crypto.dll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:)请报告是否有人得到错误的结果:)

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.确保引用System.Security.Cryptography命名空间.

RNGCryptoServiceProvider rng = new RNGCryptoServiceProvider();        

byte[] salt = new byte[16];

rng.GetBytes(salt);