The Best Seed for Random Numbers

[Leon]

I know by default the random number generator use the time, but what is the
best seed I can used in my web application?

The Program generate 6 unique random numbers and load each of them in a
textbox control. I need a good seed like ip address or something.

'Function to generate random numbers

Public Function GetRandomNumber() As Integer

Dim objRandom As New System.Random

Return objRandom.Next(1, 26)

End Function

 

[vMike]

I know by default the random number generator use the time, but what is the
best seed I can used in my web application?

The Program generate 6 unique random numbers and load each of them in a
textbox control. I need a good seed like ip address or something.

'Function to generate random numbers

Public Function GetRandomNumber() As Integer

Dim objRandom As New System.Random

Return objRandom.Next(1, 26)

End Function

I don't know if this is best or not but I use (this is for a random number
in string format) Also you can change the 8 to a higher number for a larger
random number.

Dim strID as string = DateTime.Now.Ticks.tostring()
Dim rdm1 as Random
rdm1 = new Random(ctype(right(strID,8),int32))
strUnique = rdm1.next().tostring()

 

[Scott M.]

Why take ticks (long) and cast as a string only to cast it back to an
Integer?
Why take only the right 8 chars and not the whole value?

Dim myRandom As New Random(CType(Now.Ticks, Integer))

dim theNumber as Integer = myRandom.Next

 

[vMike]

Why take ticks (long) and cast as a string only to cast it back to an
Integer?
Why take only the right 8 chars and not the whole value?

Dim myRandom As New Random(CType(Now.Ticks, Integer))

dim theNumber as Integer = myRandom.Next

Well I do this because I wanted a 16 character string and later on in the
code (not included) I add the remaining characters. Also I think if you use
the whole tick it was too big for Random.

 

[vMike]

Why take ticks (long) and cast as a string only to cast it back to an
Integer?
Why take only the right 8 chars and not the whole value?

Dim myRandom As New Random(CType(Now.Ticks, Integer))

dim theNumber as Integer = myRandom.Next

Also, the help on Random says

However, if your application runs on a fast computer the system clock might
not have time to change between invocations of this constructor; the seed
value might be the same for different instances of Random. In that case,
apply an algorithm to differentiate the seed value in each invocation.

 

[Guest]

Well, you can take a look at the .NET RNGCryptoServiceProvider.
This example is taken right off of MSDN:

Dim random() As Byte = New Byte(100) {}

'RNGCryptoServiceProvider is an implementation of an RNG
Dim rng As New RNGCryptoServiceProvider()
rng.GetBytes(random) ' bytes in random are now random

Take a look at this, it may be what you were looking for

 

[Leon]

Don't using the RNGCryptoServiceProvider slow down the web application?

 

[Guest]

So there is definately a trade off then. This is the one thing I don't like
about technology...there is no perfect solution. There is a gotcha when
doing something. Well, I guess thats live in general.lol!

 

[Leon]

This code works great, but it looks wrong. What do you see?
'Function to generate random numbers

Public Function GetRandomNumber() As Integer

Dim random() As Byte = New Byte(100) {}

'RNGCryptoServiceProvider is an implementation of an RNG

Dim rng As New RNGCryptoServiceProvider

rng.GetBytes(random) ' bytes in random are now random

Dim objRandom As New System.Random(CInt(random(100)))

Return objRandom.Next(1, 26)

End Function

 

[Scott M.]

But casting to a string and taking the last 8 chars isn't going to change
the seed value if ticks is the same for 2 calls.

Also, by casting ticks to Integer (normally long), you are shrinking it down
to an acceptable seed value.

 

[vMike]

But casting to a string and taking the last 8 chars isn't going to change
the seed value if ticks is the same for 2 calls.

Also, by casting ticks to Integer (normally long), you are shrinking it down
to an acceptable seed value.

You are right. After I posted it I realized it didn't make sense. I did have
trouble with random when using the full tick and that is why I changed it. I
see your point.