[hiker]

Integer factorization is also reducible to Knapsack:

To factorize integer N invoke a Knapsack solver with knapsack size of log(N) and items of size logarithm of all prime numbers up to sqrt(N): [log 2, log 3, log 5, ...].

If N=pq (say p and q are prime) then log(N)=log(p)+log(q).

So from all possible items in the item set, only log(p) and log(q) will fill the knapsack as tight as possible leaving zero empty space in it.

[stevefan1999]

Well, you mentioned integer factorization, that immediately leads me to RSA, which then leads me to PKI, and then leads me to cryptosystem. Combining it with the Knapsack problem, I was ultimately there for MH knapsack cryptosystem, which is unfortunately cracked [1].

[1]: https://en.wikipedia.org/wiki/Merkle%E2%80%93Hellman_knapsac...