Number of hash functions is meaningless characteristic. If your hashtable is 1GB i.e. 8GBits large, you need single 33-bit hash function to address arbitrary hashtable bit. I recommend you to try Siphash, what is 64-bit, cryptographically strong and extremely fast. Use 33It's keyed so you can use as many Siphash'es as you need, each providing 64 bits of this hash to mark bits in the table.variability
