We want to create an ICO where investors can purchase ERC20 tokens anytime but have to wait for atleast 3 months from the date of purchase in order to redeem/encash them on our platform.
But we do not intend to restrict the investors from trading /transferring/exchanging tokens among each other outside our platform.
Example 1) A buys 400 ERC20 tokens on 14th January. He sells 200 tokens to B (outside our platform) on 15th March. C buys 200 tokens on 15th March from the platform.
Now, A, B and C comes to redeem / encash the tokens for FIAT on our platform on 15th April (after 3 months from initial purchase of tokens)
Now, both A and B should be able to encash / redeem the tokens as both came to redeem after 3 months of original purchase of those tokens. But C cannot redeem it as 3 months are not over from the date of purchase.
How can we achieve this? Can we bind timestamp or any parameter with tokens or something? What is the best possible solution?