Pseudorandom vs quasi-random I'm implementing an encryption algorithm that requires me to use a random number to mix up the values. However I'm caught in between if I should use quasi-random or pseudorandom. 

These are the things I'm thinking about:


quasi-random isn't really a random number generator by definition but it's a good substitute for a uniform random  number generator, especially in the area of sampling across a plane and mathematically speaking it's more uniform compared to a uniform number generator. 
pseudorandom on the other hand by definition is random. But if the attacker knows the seed its clearly not random also. And because it is less uniform compared to quasi-random it presents a certain bias towards a certain group of numbers.


So is randomness or the uniform distribution more valued when generating a random number? Should I choose a PRNG or a quasi-random number generator?
I'm implementing an encryption algorithm that requires me to use a random number to mix up the values. However I'm caught in between if I should use quasi-random or pseudorandom.


It may sound counterintuitive, but what works best within an encryption algorithm does in fact depend on the details of that algorithm.  It may be that, for your encryption algorithm, a uniform random distribution has a nonnegligible probability of creating a weak transform, and a tailored nonuniform ("quasirandom") distribution is better.

I assume you have spent a lot of time exhaustively cryptanalyzing your encryption algorithm; what does that analysis say?

And, by the way:


  And because it is less uniform compared to quasi-random it presents a certain bias towards a certain group of numbers.


Actually, that's not accurate; the definition of a uniform distribution (which is the name of the distribution that an unbiased random number generator generates) is that it doesn't have a bias.  For example, consider the probability that a generator proceduces two consecutive outputs $7, 7$.  If the generator was uniform, the probability of those two outputs is precisely the same as the probability of producing any other two specified outputs.  However, if the generator is quasirandom, the probability may be significantly smaller (even 0), if the quasirandom generator was biased away from repeating outputs.