Custom Hash Algorithm

Question

Is it possible to create a custom hash algorithm, something that can provide an integer within a specific range. Example below.

(a,b) is the input to the hash. (a,b) != (b,a) where a and b are both integers >= 0

The solution must be within the range (min,max).

Would this be possible? With this I would like (a,b) being hashed on two occasions to provide the same integer if also being given the same range as well.

Thank you.

Yes, of course it would be possible. Why don't you try writing one? — Dawood ibn Kareem
– Dawood ibn Kareem, Commented Nov 5, 2017 at 22:11
You could start from here: hashCode() and to get numbers between a specific range you can use modular arithmetic — user5955745
– user5955745, Commented Nov 5, 2017 at 22:17
It's impossible to guarantee that (a,b) != (b,a). Hashes aren't collision-proof. — shmosel
– shmosel, Commented Nov 5, 2017 at 22:43
@shmosel It's absolutely possible to guarantee that, whenever a != b. Consider the function (a,b) -> ( a > b ? 1 : 0 ) — Dawood ibn Kareem
– Dawood ibn Kareem, Commented Nov 6, 2017 at 1:58

Fermat's Little Student · Accepted Answer · 2017-11-05 22:11:40Z

1

(a,b) is the input to the hash. (a,b) != (b,a) where a and b are both integers >= 0

No. Suppose a = b, then (a,b) = (b,a). This constraint violates consistency of hashing therefore impossible

answered Nov 5, 2017 at 22:11

Fermat's Little Student

6,3697 gold badges53 silver badges70 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Jamie Over a year ago

That is a good point. What if we assumed that (a,b) cannot equal (b,a) except for in the case that they were equal? Or would assume that was the case in that one situation make it impossible as well?

Fermat's Little Student Over a year ago

@Jamie Then it is possible. But it will be hard to find a good one if (a, b) != (a, b) for all a, b. The easiest solution would be simply a - b. But this isn't a good one because it may not be uniformly distributed if a and b have some pattern. To address the min, max range issue is rather easy. Just transfrom your hash h into min + h % p, where p is some prime no greater than (max - min)

Collectives™ on Stack Overflow

Custom Hash Algorithm

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related