How can I rewrite the password hash made by SHA1 (in ASP.NET Identity)?

Question

I used SHA1 to hash passwords on my site. I am trying to switch to ASP.NET Identity. I found how I can verify old passwords ( ASP.NET Identity default Password Hasher, how does it work and is safe? ):

public class CustomPasswordHasher : IPasswordHasher
{
 //....
  public static bool VerifyHashedPassword(string hashedPassword, string password)
  {
    byte[] buffer4;
    if (hashedPassword == null)
    {
        return false;
    }
    if (password == null)
    {
        throw new ArgumentNullException("password");
    }
// Old hash verification
    using (SHA1Managed sha1 = new SHA1Managed())
    {
      var hash = sha1.ComputeHash(Encoding.UTF8.GetBytes(password));
      var sb = new StringBuilder(hash.Length * 2);

      foreach (byte b in hash)
      {
          sb.Append(b.ToString("x2"));
      }

      if(hashedPassword == sb.ToString()) return true;
      else return false;
    }

// Identity hash verification
    byte[] src = Convert.FromBase64String(hashedPassword);
    if ((src.Length != 0x31) || (src[0] != 0))
    {
        return false;
    }
    byte[] dst = new byte[0x10];
    Buffer.BlockCopy(src, 1, dst, 0, 0x10);
    byte[] buffer3 = new byte[0x20];
    Buffer.BlockCopy(src, 0x11, buffer3, 0, 0x20);
    using (Rfc2898DeriveBytes bytes = new Rfc2898DeriveBytes(password, dst, 0x3e8))
    {
        buffer4 = bytes.GetBytes(0x20);
    }
        return ByteArraysEqual(buffer3, buffer4);
  }
//....
}

In my custom ApplicationUserManager, I set the PasswordHasher property:

//....
manager.PasswordHasher = new CustomPasswordHasher();
//....

Now I would like to delete the old hash (sha1) and save the new hash. How can i do this?

Thanks in advance!

Answer 1

, - SHA1. SHA1 .

, . :

public void Login(String username, String password)
{
    if(DoesOldHashMatch(username, password)){
        var newHash = NewHasher.GetPasswordHash(password);
        UpdateUserPasswordHash(username, newHash);
        SetLoginCookie(username);
        return;
    }
    if(NewHashMatch(username, password))
    {
        SetLoginCookie(username);
    }
}