Issue with crypt_gen

-- This runs for about 50s on my computer.
declare @t table (Number int)
declare @winners table (Number int)
declare @i int = 0
declare @iCount int = 10
declare @j int = 0
declare @jCount int = 100000

while (@i < @iCount)
begin
delete from @t
set @j = 0
while (@j < @jCount)
begin
insert into @t (Number)
select dbo.GetRandom(1, 3)

set @j += 1
end

insert into @winners (Number)
select top 1 Number
from (
select Number, count(*) C
from @t
group by Number
) x
order by C desc

set @i += 1
end

select Number, count(*)
from @winners
group by Number
order by count(*) desc

_simon_ (2/1/2013)

This is my scalar function, which returns numbers between @min and @max (both included):

create function GetRandom(@min int, @max int)
	returns int
as
begin
	declare @diff int = @max - @min + 1
	return @min + crypt_gen_random(1) % @diff
end

This is how I test it:

-- This runs for about 50s on my computer.
declare @t table (Number int)
declare @winners table (Number int)
declare @i int = 0
declare @iCount int = 10
declare @j int = 0
declare @jCount int = 100000

while (@i < @iCount)
begin
	delete from @t
	set @j = 0
	while (@j < @jCount)
	begin
		insert into @t (Number)
		select dbo.GetRandom(1, 3)
		
		set @j += 1
	end

	insert into @winners (Number)
	select top 1 Number
	from (
		select Number, count(*) C
		from @t
		group by Number
	) x
	order by C desc
	
	set @i += 1
end

select Number, count(*)
from @winners
group by Number
order by count(*) desc

Output (number 1 wins in ~80% cases):

Number      
----------- -----------
1           9
2           1

Now almost every time I run this query, the Number 1 appears slightly more often... Is there something wrong with my GetRandom function?

Microsoft SQL Server 2008 R2 (SP1) - 10.50.2500.0 (X64)
Jun 17 2011 00:54:03
Copyright (c) Microsoft Corporation
Standard Edition (64-bit) on Windows NT 6.1 <X64> (Build 7601: Service Pack 1) (Hypervisor)

-- Data definition and setup
DECLARE @NumberOfRNs INT

SELECT @NumberOfRNs = 100

--CREATE TYPE Distribution AS TABLE (EventID INT, EventProb FLOAT, CumProb FLOAT)
DECLARE @Binomial AS Distribution

-- Simulate a coin toss with a Binomial Distribution
INSERT INTO @Binomial
SELECT 0, 0.5, 0.5 UNION ALL SELECT 1, 0.5, 1.0

-- Create random numbers for the selected distributions
SELECT TOP (@NumberOfRNs)
RandomBinomial = dbo.RN_MULTINOMIAL(@Binomial, URN)
INTO #MyRandomNumbers
FROM sys.all_columns a1 CROSS APPLY sys.all_columns a2
CROSS APPLY (SELECT RAND(CHECKSUM(NEWID()))) URN(URN)

SELECT RandomBinomial, Number=COUNT(RandomBinomial)
FROM #MyRandomNumbers
GROUP BY RandomBinomial

DROP TABLE #MyRandomNumbers

--CREATE TYPE Distribution AS TABLE (EventID INT, EventProb FLOAT, CumProb FLOAT)

DECLARE @Binomial AS Distribution
DECLARE @MinNumber INT = 50, @MaxNumber INT = 500

;WITH Tally AS (
SELECT n=number
FROM [master].dbo.spt_values Tally
WHERE [Type] = 'P' AND Number BETWEEN @MinNumber AND @MaxNumber)
INSERT INTO @Binomial
SELECT n, 1./(1+@MaxNumber-@MinNumber), (1.+n-@MinNumber)/(1.+@MaxNumber-@MinNumber)
FROM Tally

SELECT *
FROM @Binomial

[SqlFunction]
public static int RndBetween(int minValue, int maxValue)
{
if (minValue > maxValue) throw new ArgumentOutOfRangeException("minValue");
if (minValue == maxValue) return minValue;

// Make maxValue inclusive.
maxValue++;

var rng = new RNGCryptoServiceProvider();
var uint32Buffer = new byte[4];
long diff = maxValue - minValue;

while (true)
{
rng.GetBytes(uint32Buffer);
uint rand = BitConverter.ToUInt32(uint32Buffer, 0);
const long max = (1 + (long)int.MaxValue);
long remainder = max % diff;
if (rand < max - remainder)
{
return (int)(minValue + (rand % diff));
}
}
}