This process does not alter the original key-space entropy. The key stretching algorithm is deterministic, allowing a weak input to always generate the same enhanced key, but therefore limiting the enhanced key to no more possible combinations than the input key space. Consequently, this attack remains vulnerable if unprotected against certain time-memory tradeoffs such as developing rainbow tables to target multiple instances of the enhanced key space in parallel (effectively a "shortcut" to repeating the algorithm). For this reason, key stretching is often combined with salting.