Comparing two values without revealing them Suppose Alice wants to prove to Bob that t1 is less than t2. t1 and t2 represent timestamps. Alice does not want to reveal t1 and t2. However, she needs to receive Bob’s confirmation that t1 &lt; t2. In order to prevent Bob from performing a brute-force attack to find t1 and t2, Alice wants to use some salt with the timestamps. 

Any idea how to use cryptographic algorithms in order to solve this problem?
From the last part of your question, I understand that you need order preserving hash function or encryption. Look into this thread
How does order-preserving encryption work?