Use RandomNumberGenerator instead of System.Random

Needed for an internal assessment task.

Xamarin.MacDev/SQLite.cs

@@ -31,6 +31,7 @@
 using System.Linq;
 using System.Linq.Expressions;
 using System.Threading;
+using System.Security.Cryptography;
 
 #if USE_CSHARP_SQLITE
 using Sqlite3 = Community.CsharpSqlite.Sqlite3;
@@ -93,7 +94,7 @@ public partial class SQLiteConnection : IDisposable {
 		private long _elapsedMilliseconds = 0;
 
 		private int _transactionDepth = 0;
-		private Random _rand = new Random ();
+		private RandomNumberGenerator _rand = RandomNumberGenerator.Create();
 
 		public Sqlite3DatabaseHandle Handle { get; private set; }
 		internal static readonly Sqlite3DatabaseHandle NullHandle = default (Sqlite3DatabaseHandle);
@@ -855,7 +856,11 @@ public void BeginTransaction ()
 		public string SaveTransactionPoint ()
 		{
 			int depth = Interlocked.Increment (ref _transactionDepth) - 1;
-			string retVal = "S" + _rand.Next (short.MaxValue) + "D" + depth;
+			byte[] random = new byte[2];
+
+			_rand.GetNonZeroBytes (random);
+			var sv = BitConverter.ToUInt16 (random, 0);
+			string retVal = "S" + sv + "D" + depth;
 
 			try {
 				Execute ("savepoint " + retVal);
@@ -1391,6 +1396,9 @@ public void Dispose ()
 
 		protected virtual void Dispose (bool disposing)
 		{
+			if (disposing)
+				_rand.Dispose ();
+
 			Close ();
 		}