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Cryptographically-strong random number generator in C#.
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| // Cryptographically-strong random number generator | |
| // Source: MSDN Magazine > 2007 > September > .NET Matters: Tales from the CryptoRandom | |
| // Source URL: http://msdn.microsoft.com/en-us/magazine/cc163367.aspx | |
| // Authors: Stephen Toub & Shawn Farkas | |
| public class CryptoRandom : Random | |
| { | |
| private RNGCryptoServiceProvider cryptoProvider = new RNGCryptoServiceProvider(); | |
| private byte[] uint32Buffer = new byte[4]; | |
| /// <summary> | |
| /// An implementation of System.Random used for cryptographically-strong random number generation. | |
| /// </summary> | |
| public CryptoRandom() { } | |
| /// <summary> | |
| /// An implementation of System.Random used for cryptographically-strong random number generation. | |
| /// </summary> | |
| public CryptoRandom(Int32 seedIgnored) { } | |
| /// <summary> | |
| /// Returns a nonnegative random number. | |
| /// </summary> | |
| /// <returns> | |
| /// A 32-bit signed integer greater than or equal to zero and less than <see cref="F:System.Int32.MaxValue"/>. | |
| /// </returns> | |
| public override Int32 Next() | |
| { | |
| cryptoProvider.GetBytes(uint32Buffer); | |
| return BitConverter.ToInt32(uint32Buffer, 0) & 0x7FFFFFFF; | |
| } | |
| /// <summary> | |
| /// Returns a nonnegative random number less than the specified maximum. | |
| /// </summary> | |
| /// <returns> | |
| /// A 32-bit signed integer greater than or equal to zero, and less than <paramref name="maxValue"/>; that is, the range of return values ordinarily includes zero but not <paramref name="maxValue"/>. However, if <paramref name="maxValue"/> equals zero, <paramref name="maxValue"/> is returned. | |
| /// </returns> | |
| /// <param name="maxValue">The exclusive upper bound of the random number to be generated. <paramref name="maxValue"/> must be greater than or equal to zero.</param> | |
| /// <exception cref="T:System.ArgumentOutOfRangeException"><paramref name="maxValue"/> is less than zero.</exception> | |
| public override Int32 Next(Int32 maxValue) | |
| { | |
| if (maxValue < 0) throw new ArgumentOutOfRangeException("maxValue"); | |
| return Next(0, maxValue); | |
| } | |
| /// <summary> | |
| /// Returns a random number within a specified range. | |
| /// </summary> | |
| /// <returns> | |
| /// A 32-bit signed integer greater than or equal to <paramref name="minValue"/> and less than <paramref name="maxValue"/>; that is, the range of return values includes <paramref name="minValue"/> but not <paramref name="maxValue"/>. If <paramref name="minValue"/> equals <paramref name="maxValue"/>, <paramref name="minValue"/> is returned. | |
| /// </returns> | |
| /// <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. <paramref name="maxValue"/> must be greater than or equal to <paramref name="minValue"/>.</param> | |
| /// <exception cref="T:System.ArgumentOutOfRangeException"><paramref name="minValue"/> is greater than <paramref name="maxValue"/>.</exception> | |
| public override Int32 Next(Int32 minValue, Int32 maxValue) | |
| { | |
| if (minValue > maxValue) throw new ArgumentOutOfRangeException("minValue"); | |
| if (minValue == maxValue) return minValue; | |
| Int64 diff = maxValue - minValue; | |
| while (true) | |
| { | |
| cryptoProvider.GetBytes(uint32Buffer); | |
| UInt32 rand = BitConverter.ToUInt32(uint32Buffer, 0); | |
| Int64 max = (1 + (Int64)UInt32.MaxValue); | |
| Int64 remainder = max % diff; | |
| if (rand < max - remainder) | |
| { | |
| return (Int32)(minValue + (rand % diff)); | |
| } | |
| } | |
| } | |
| /// <summary> | |
| /// Returns a random number between 0.0 and 1.0. | |
| /// </summary> | |
| /// <returns> | |
| /// A double-precision floating point number greater than or equal to 0.0, and less than 1.0. | |
| /// </returns> | |
| public override double NextDouble() | |
| { | |
| cryptoProvider.GetBytes(uint32Buffer); | |
| UInt32 rand = BitConverter.ToUInt32(uint32Buffer, 0); | |
| return rand / (1.0 + UInt32.MaxValue); | |
| } | |
| /// <summary> | |
| /// Fills the elements of a specified array of bytes with random numbers. | |
| /// </summary> | |
| /// <param name="buffer">An array of bytes to contain random numbers.</param> | |
| /// <exception cref="T:System.ArgumentNullException"><paramref name="buffer"/> is null. | |
| public override void NextBytes(byte[] buffer) | |
| { | |
| if (buffer == null) throw new ArgumentNullException("buffer"); | |
| cryptoProvider.GetBytes(buffer); | |
| } | |
| } |
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