RNGCryptoServiceProvider - 随机数查看

Question

在寻找生成真正随机数的最佳尝试时，我偶然发现了这个代码示例。

在此片段中寻找意见。

using System;
using System.Security.Cryptography;

private static int NextInt(int min, int max)
{
    RNGCryptoServiceProvider rng = new RNGCryptoServiceProvider();
    byte[] buffer = new byte[4];

    rng.GetBytes(buffer);
    int result = BitConverter.ToInt32(buffer, 0);

    return new Random(result).Next(min, max);
}

来源：http://www.vcskicks.com/code-snippet/rng-int.php

这比使用滴答计数种子更受欢迎，例如：

Random rand = new Random(Environment.TickCount); 
rand.Next(min, max);

注意：

我不是在寻找第三方随机数据提供程序，例如Random.org，因为这种依赖对应用程序来说是不现实的。

Answer 1

好吧，使用RNGCryptoServiceProvider会给你一个不可思议的加密强度种子，而Environment.TickCount在理论上是可预测的。

在快速连续多次调用NextInt方法时，另一个重要区别是显而易见的。使用RNGCryptoServiceProvider将每次使用不同的加密强度数对Random对象进行播种，这意味着它将继续为每个调用返回不同的随机数。使用TickCount冒险每次都使用相同的数字播种Random对象（如果在相同的“tick”期间多次调用该方法），这意味着它将继续返回相同的（假设是随机的） ）每次通话的号码。

如果您确实需要真正的随机数，那么您根本不应该使用计算机来生成它们：您应该测量放射性衰变或类似的东西，真正无法预测。

Answer 2

不要使用您的代码。您的解决方案是错误的，并产生差的随机数。我建议我的解决方案，它生成加密强大的随机数：

public class SecureRandom : RandomNumberGenerator
{
    private readonly RandomNumberGenerator rng = new RNGCryptoServiceProvider();


    public int Next()
    {
        var data = new byte[sizeof(int)];
        rng.GetBytes(data);
        return BitConverter.ToInt32(data, 0) & (int.MaxValue - 1);
    }

    public int Next(int maxValue)
    {
        return Next(0, maxValue);
    }

    public int Next(int minValue, int maxValue)
    {
        if (minValue > maxValue)
        {
            throw new ArgumentOutOfRangeException();
        }
        return (int)Math.Floor((minValue + ((double)maxValue - minValue) * NextDouble()));
    }

    public double NextDouble()
    {
        var data = new byte[sizeof(uint)];
        rng.GetBytes(data);
        var randUint = BitConverter.ToUInt32(data, 0);
        return randUint / (uint.MaxValue + 1.0);
    }

    public override void GetBytes(byte[] data)
    {
        rng.GetBytes(data);
    }

    public override void GetNonZeroBytes(byte[] data)
    {
        rng.GetNonZeroBytes(data);
    }
}

Answer 3

我问了similar question 2年前:)检查一下它是否对你有所帮助。我使用该代码生成用于支付处理的安全随机数。

Answer 4

我真的不建议使用提供的示例。虽然RNGCryptoServiceProvider返回真正好的随机（或至少它应该），但对于Random来说同样如此。更多 - 不知道Random（value）是否为Next（..）重新调整的值创建了真正的双射。更多 - 不能保证Next（min，max）以真正随机的方式返回值（意味着数字命中每个值的机会相等）。

我会首先将问题推迟到0区间的数字 - 最大（不包括）。然后我将使用最接近2的幂来获得0 - （2 ^ n - 1）范围内的随机值。现在你必须做的一件事就是使用modulo来获得优先范围内的数字，如rand（0 - （2 ^ n - 1））％max，因为通过这样做你实际上增加了在较低范围内编号的机会。 / p>

示例 - max = 3，n = 2（0 - （2 ^ 2 - 1））％2，数字（0,1,2,3），模数后的对应值（0,1,2,0） 。看到我们两次击中0，这实际上是糟糕的随机。

因此，解决方案是使用加密随机获取最接近2的幂，如果值超出最大范围，重复进行（获得另一个加密随机），直到值在给定范围内。这将是更好的algorythm。

Answer 5

我认为这是一个比上面列出的更高效，可能更快的发生器。

public static class SecureRandom
{
    #region Constants
    private const int INT_SIZE = 4;
    private const int INT64_SIZE = 8;
    #endregion

    #region Fields
    private static RandomNumberGenerator _Random;
    #endregion

    #region Constructor
    static SecureRandom()
    {
        _Random = new RNGCryptoServiceProvider();
    }
    #endregion

    #region Random Int32
    /// <summary>
    /// Get the next random integer
    /// </summary>
    /// <returns>Random [Int32]</returns>
    public static Int32 Next()
    {
        byte[] data = new byte[INT_SIZE];
        Int32[] result = new Int32[1];

        _Random.GetBytes(data);
        Buffer.BlockCopy(data, 0, result, 0, INT_SIZE);

        return result[0];
    }

    /// <summary>
    /// Get the next random integer to a maximum value
    /// </summary>
    /// <param name="MaxValue">Maximum value</param>
    /// <returns>Random [Int32]</returns>
    public static Int32 Next(Int32 MaxValue)
    {
        Int32 result = 0;

        do
        {
            result = Next();
        } while (result > MaxValue);

        return result;
    }
    #endregion

    #region Random UInt32
    /// <summary>
    /// Get the next random unsigned integer
    /// </summary>
    /// <returns>Random [UInt32]</returns>
    public static UInt32 NextUInt()
    {
        byte[] data = new byte[INT_SIZE];
        Int32[] result = new Int32[1];

        do
        {
            _Random.GetBytes(data);
            Buffer.BlockCopy(data, 0, result, 0, INT_SIZE);
        } while (result[0] < 0);

        return (UInt32)result[0];
    }

    /// <summary>
    /// Get the next random unsigned integer to a maximum value
    /// </summary>
    /// <param name="MaxValue">Maximum value</param>
    /// <returns>Random [UInt32]</returns>
    public static UInt32 NextUInt(UInt32 MaxValue)
    {
        UInt32 result = 0;

        do
        {
            result = NextUInt();
        } while (result > MaxValue);

        return result;
    }
    #endregion

    #region Random Int64
    /// <summary>
    /// Get the next random integer
    /// </summary>
    /// <returns>Random [Int32]</returns>
    public static Int64 NextLong()
    {
        byte[] data = new byte[INT64_SIZE];
        Int64[] result = new Int64[1];

        _Random.GetBytes(data);
        Buffer.BlockCopy(data, 0, result, 0, INT64_SIZE);

        return result[0];
    }

    /// <summary>
    /// Get the next random unsigned long to a maximum value
    /// </summary>
    /// <param name="MaxValue">Maximum value</param>
    /// <returns>Random [UInt64]</returns>
    public static Int64 NextLong(Int64 MaxValue)
    {
        Int64 result = 0;

        do
        {
            result = NextLong();
        } while (result > MaxValue);

        return result;
    }
    #endregion

    #region Random UInt32
    /// <summary>
    /// Get the next random unsigned long
    /// </summary>
    /// <returns>Random [UInt64]</returns>
    public static UInt64 NextULong()
    {
        byte[] data = new byte[INT64_SIZE];
        Int64[] result = new Int64[1];

        do
        {
            _Random.GetBytes(data);
            Buffer.BlockCopy(data, 0, result, 0, INT64_SIZE);
        } while (result[0] < 0);

        return (UInt64)result[0];
    }

    /// <summary>
    /// Get the next random unsigned long to a maximum value
    /// </summary>
    /// <param name="MaxValue">Maximum value</param>
    /// <returns>Random [UInt64]</returns>
    public static UInt64 NextULong(UInt64 MaxValue)
    {
        UInt64 result = 0;

        do
        {
            result = NextULong();
        } while (result > MaxValue);

        return result;
    }
    #endregion

    #region Random Bytes
    /// <summary>
    /// Get random bytes
    /// </summary>
    /// <param name="data">Random [byte array]</param>
    public static byte[] NextBytes(long Size)
    {
        byte[] data = new byte[Size];
        _Random.GetBytes(data);
        return data;
    }
    #endregion
}

Answer 6

我觉得这可能会更简单，并且可以用更少的代码行实现，所以我将投入更多精力-这将始终返回0到1之间的正数。

public double Random()
{
    using var csp = new RNGCryptoServiceProvider();

    byte[] b = new byte[8];
    csp.GetBytes(b);
    var lng = BitConverter.ToInt64(b, 0);
    var dbl = (double)(lng < 0 ? ~lng : lng);

    // Convert to a random number between 0 and 1
    return dbl / long.MaxValue;
}

代替每次都创建一个新的RNGCryptoServiceProvider，一个简单的静态字段就可以了。

要返回两个数字之间的随机正整数，这可以正常工作-尽管您需要检查min小于max，并且两者都为正数：

public long RandomInt64(long min = 0, long max = long.MaxValue)
{
    // Check arguments
    if (min >= max)
    {
        throw new ArgumentOutOfRangeException(nameof(min), min, "Minimium value must be less than the maximum value.");
    }

    if (min < 0)
    {
        throw new ArgumentException("Minimum value must be at least 0.", nameof(min));
    }

    // Get the range between the specified minimum and maximum values
    var range = max - min;

    // Now add a random amount of the range to the minimum value - it will never exceed maximum value
    var add = Math.Round(range * Random());
    return (long)(min + add);
}

Answer 7

这实际上取决于生成的随机数的预期用途或要求。

Random类对于实际随机化很有用，例如随机化图像旋转器中的订单图像显示或模具卷。
另一方面，如果您需要需要更高安全性的随机数，例如生成密码或付款确认密钥，则使用诸如RNGCryptoServiceProvider之类的类或创建您自己的抽象类实现{{实现加密算法的3}}是更好的选择。

Answer 8

好的，所以我来晚了一点，但我真的想要一个完整的System.Random实现，可以在同一个计时器tic中多次调用并产生不同的结果。在对不同的实现感到非常痛苦之后，我决定使用我提出的最简单的一个，它提供了一个默认构造函数，它为基本System.Random构造函数提供随机密钥：

/// <summary> An implementation of System.Random whose default constructor uses a random seed value rather than the system time. </summary>
public class RandomEx : Random
{
    /// <summary> Initializes a new CryptoRandom instance using a random seed value. </summary>
    public RandomEx()
        : base(_GetSeed())
    { }

    /// <summary> Initializes a new CryptoRandom instance using the specified seed value. </summary>
    /// <param name="seed"> The seed value. </param>
    public RandomEx(int seed)
        : base(seed)
    { }

    // The static (shared by all callers!) RandomNumberGenerator instance
    private static RandomNumberGenerator _rng = null;

    /// <summary> Static method that returns a random integer. </summary>
    private static int _GetSeed()
    {
        var seed = new byte[sizeof(int)];

        lock (typeof(RandomEx)) {
            // Initialize the RandomNumberGenerator instance if necessary
            if (_rng == null) _rng = new RNGCryptoServiceProvider();

            // Get the random bytes
            _rng.GetBytes(seed);
        }

        // Convert the bytes to an int
        return BitConverter.ToInt32(seed, 0);
    }
}

在此过程中，我还编写并测试了一个实现，该实现覆盖了使用RNGCryptoServiceProvider提供所有随机值所必需的方法（而不是依赖于随机数生成器被捆绑到System.Random类中）。但是，当你获取我的随机Sample（）值并通过转换推送产生整数值时，我不知道结果是如何加密的。无论如何，这是代码，如果有人想要它：

/// <summary> An implementation of System.Random that uses RNGCryptoServiceProvider to provide random values. </summary>
public class CryptoRandom : Random, IDisposable
{
    // Class data
    RandomNumberGenerator _csp = new RNGCryptoServiceProvider();

    /// <summary> Returns a random number between 0.0 (inclusive) and 1.0 (exclusive). </summary>
    protected override double Sample()
    {
        // Get a nonnegative random Int64
        byte[] bytes = new byte[sizeof(long)];
        _csp.GetBytes(bytes);
        long value = BitConverter.ToInt64(bytes, 0) & long.MaxValue;

        // Scale it to 0->1
        return (double)value / (((double)Int64.MaxValue) + 1025.0d);
    }

    /// <summary> Fills the elements of the specified array of bytes with random numbers. </summary>
    /// <param name="buffer"> An array of bytes to contain random numbers. </param>
    public override void NextBytes(byte[] buffer)
    {
        _csp.GetBytes(buffer);
    }

    /// <summary> Returns a nonnegative random integer. </summary>
    /// <returns> A 32-bit signed integer greater than or equal to zero. </returns>
    public override int Next()
    {
        byte[] data = new byte[4];
        _csp.GetBytes(data);
        data[3] &= 0x7f;
        return BitConverter.ToInt32(data, 0);
    }

    /// <summary> Returns a random integer that is within a specified range. </summary>
    /// <param name="minValue"> The inclusive lower bound of the random number returned. </param>
    /// <param name="maxValue"> The exclusive upper bound of the random number returned. maxValue must be greater than or equal to minValue. </param>
    /// <returns> A 32-bit signed integer greater than or equal to minValue and less than maxValue; that is, the range of return values includes minValue but not maxValue. If minValue equals maxValue, minValue is returned. </returns>
    public override int Next(int minValue, int maxValue)
    {
        // Special case
        if (minValue == maxValue) return minValue;

        double sample = Sample();
        double range = (double)maxValue - (double)minValue;
        return (int)((sample * (double)range) + (double)minValue);
    }

    #region IDisposible implementation

    /// <summary> Disposes the CryptoRandom instance and all of its allocated resources. </summary>
    public void Dispose()
    {
        // Do the actual work
        Dispose(true);

        // This object will be cleaned up by the Dispose method. Call GC.SupressFinalize to 
        // take this object off the finalization queue and prevent finalization code for this object 
        // from executing a second time.
        GC.SuppressFinalize(this);
    }

    // Dispose(bool disposing) executes in two distinct scenarios:
    //
    // If disposing is true, the method has been called directly or indirectly by a user's code and both
    // managed and unmanaged resources can be disposed. 
    //
    // If disposing is false, the method has been called by the runtime from inside the finalizer.
    // In this case, only unmanaged resources can be disposed. 
    protected virtual void Dispose(bool disposing)
    {
        if (disposing) {
            // The method has been called directly or indirectly by a user's code; dispose managed resources (if any)
            if (_csp != null) {
                _csp.Dispose();
                _csp = null;
            }

            // Dispose unmanaged resources (if any)
        }
    }

    #endregion
}