問題描述

我想在 c# 中使用 Rfc2898 來派生密鑰.我還需要使用 SHA256 作為 Rfc2898 的摘要.我找到了類 Rfc2898DeriveBytes，但它使用 SHA-1，我看不出有辦法讓它使用不同的摘要.

I want to use Rfc2898 in c# to derive a key. I also need to use SHA256 as Digest for Rfc2898. I found the class Rfc2898DeriveBytes, but it uses SHA-1 and I don't see a way to make it use a different digest.

有沒有辦法在 c# 中使用 Rfc2898 和 SHA256 作為摘要(沒有從頭開始實現它)?

Is there a way to use Rfc2898 in c# with SHA256 as digest (short of implementing it from scratch)?

推薦答案

查看 Bruno Garcia 的回答.

See Bruno Garcia's answer.

Carsten:請接受那個答案而不是這個答案.

Carsten: Please accept that answer rather than this one.

在我開始回答這個問題時，Rfc2898DeriveBytes 無法配置為使用不同的哈希函數.但與此同時，它也得到了改進.見布魯諾加西亞的回答.以下函數可用于生成用戶提供的密碼的哈希版本，以存儲在數據庫中用于身份驗證.

At the time I started this answer, Rfc2898DeriveBytes was not configurable to use a different hash function. In the meantime, though, it has been improved; see Bruno Garcia's answer. The following function can be used to generate a hashed version of a user-provided password to store in a database for authentication purposes.

對于舊 .NET 框架的用戶，這仍然很有用:

For users of older .NET frameworks, this is still useful:

// NOTE: The iteration count should
// be as high as possible without causing
// unreasonable delay.  Note also that the password
// and salt are byte arrays, not strings.  After use,
// the password and salt should be cleared (with Array.Clear)

public static byte[] PBKDF2Sha256GetBytes(int dklen, byte[] password, byte[] salt, int iterationCount){
    using(var hmac=new System.Security.Cryptography.HMACSHA256(password)){
        int hashLength=hmac.HashSize/8;
        if((hmac.HashSize&7)!=0)
            hashLength++;
        int keyLength=dklen/hashLength;
        if((long)dklen>(0xFFFFFFFFL*hashLength) || dklen<0)
            throw new ArgumentOutOfRangeException("dklen");
        if(dklen%hashLength!=0)
            keyLength++;
        byte[] extendedkey=new byte[salt.Length+4];
        Buffer.BlockCopy(salt,0,extendedkey,0,salt.Length);
        using(var ms=new System.IO.MemoryStream()){
            for(int i=0;i<keyLength;i++){
                extendedkey[salt.Length]=(byte)(((i+1)>>24)&0xFF);
                extendedkey[salt.Length+1]=(byte)(((i+1)>>16)&0xFF);
                extendedkey[salt.Length+2]=(byte)(((i+1)>>8)&0xFF);
                extendedkey[salt.Length+3]=(byte)(((i+1))&0xFF);
                byte[] u=hmac.ComputeHash(extendedkey);
                Array.Clear(extendedkey,salt.Length,4);
                byte[] f=u;
                for(int j=1;j<iterationCount;j++){
                    u=hmac.ComputeHash(u);
                    for(int k=0;k<f.Length;k++){
                        f[k]^=u[k];
                    }
                }
                ms.Write(f,0,f.Length);
                Array.Clear(u,0,u.Length);
                Array.Clear(f,0,f.Length);
            }
            byte[] dk=new byte[dklen];
            ms.Position=0;
            ms.Read(dk,0,dklen);
            ms.Position=0;
            for(long i=0;i<ms.Length;i++){
                ms.WriteByte(0);
            }
            Array.Clear(extendedkey,0,extendedkey.Length);
            return dk;
        }
    }

這篇關于Rfc2898/PBKDF2 與 SHA256 作為 C# 中的摘要的文章就介紹到這了，希望我們推薦的答案對大家有所幫助，也希望大家多多支持html5模板網！