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C# RNGCryptoServiceProvider ExampleUse RNGCryptoServiceProvider to get high-quality random numbers.
RNGCryptoServiceProvider generates high-quality random numbers. With it, we use an RNG (random number generator) that is as random as possible.
This helps in applications where random numbers must be completely random. RNGCryptoServiceProvider has a cost: it reduces performance over the Random type.
Random
Example. The most useful method on RNGCryptoServiceProvider is the GetBytes method. You can enclose it in a using-statement. We fill a 4-byte array with GetBytes 10 times.
Then We use BitConverter.ToInt32 to change those 4-byte arrays into integers. This yields random integers.
BitConverter
Output The output looks random. I haven't run any tests of randomness on RNGCryptoServiceProvider or compared it to the Random type.
using System; using System.Security.Cryptography; class Program { static void Main() { using (RNGCryptoServiceProvider rng = new RNGCryptoServiceProvider()) { // Buffer storage. byte[] data = new byte[4]; // Ten iterations. for (int i = 0; i < 10; i++) { // Fill buffer. rng.GetBytes(data); // Convert to int 32. int value = BitConverter.ToInt32(data, 0); Console.WriteLine(value); } } } }
461315061 -1277834804 -1239389884 -1540126655 1669339804 1436197105 -473414988 -264059284 -1832694377 -1929982707
Benchmark. I quantified the performance of RNGCryptoServiceProvider and Random. The code called Next() for Random. The objects were created outside of the inner loop.
Result It is clear from these results that you might end up with a slow program if you overuse RNGCryptoServiceProvider.
Benchmark results:
Time for one random int from RNGCryptoServiceProvider: 2796.19 ns Time for one random int from Random: 9.30 ns
Discussion. So when should you use RNGCryptoServiceProvider? My expectation is that for most programs, Random is sufficient and preferable due to its simplicity.
But For important programs RNGCryptoServiceProvider is better because it is less prone to problems with its randomness.
Note The Random type does not use the RNGCryptoServiceProvider internally. The implementations are different.
Summary. We looked at the RNGCryptoServiceProvider type. With this type, you can fill byte arrays with random values. Then you can convert those byte arrays to integral types or use them directly.
Byte Array
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