Seeding a random number, why seed?

[j.smith1981]

Hi there,

 

I just wanted to know what seeding actually means and why one would use that?

 

I mean I kind of get it in my head but wanted to clarify my understanding, my understanding is either it takes a value and then makes that into a random other number, I heard about random numbers being psuedo numbers but why would you call them that?

 

Just out of pure interest that's all, I just can't get an example working in a book but can you help me with any other resources on the web for this that maybe explains allot better?

 

Thank you ever so much in advance,

Jeremy.

[thehippy]

Random number generators are algorithms, if you just call random random number generator function without a seed it'll fall back on its 'defaults,' typically values pulled from the system that constantly change (ex. time, pid #, mouse position, etc) those can be different from implementation to implementation, but if one knew what the default might be or a range of possible values they could greatly reduce the number of guesses they would have to make if for instance the random number was part of an encryption scheme.  Depending on the implementation, the algorithm will use the provided seed instead of the defaults or it will use the seed in addition to the defaults.

 

This is a slight distinction but seeds also used to refer to the 'set' of numbers a generator would use (ex. 1, 4, 7 and 9), so there may be some cross usage in older documentation.

 

Pseudo-random numbers stem from the fact that through computation you cannot create a real random number, its a purely procedural process.  Probably a bad way to explain it, but I can't come up with better at the moment.

 

My cryptography knowledge comes from Bruce Schneier's Applied Cryptography he co-authored a newer book Cryptography Engineering which looks like a good updated alternative.

[j.smith1981]

Ahh kind of makes sense with the way you explain the procedural process of creating sort of I mean as pseudo goes the kind of terminology is that it's not really a random number it's faking to be an random number you mean?

 

I kind of get that part now thank you (if I am thinking right about this).

 

I look forward to your or anyone elses reply on this, will look at those references though and thank you for posting them.

 

Jeremy.