Earlier, this year, we announced new features in MWC that make offline secure storage and a variant of the glacier protocol possible in MWC. We released guide to explain how to do it as well. It can be done on our testnet today. Now, as we approach the launch of mainnet, we have made even more progress on the cold storage front. Today, we released a cold storage project for the testnet (this will be updated for mainnet at the time of launch). The project can be found here: https://github.com/mwcproject/coldstorage
This project allows the user to easily implement a cold storage strategy in MWC. We give full details on how to create a bootable Ubuntu USB stick and to transfer funds to and from the cold storage using the file method of transfer in MWC. We also provide setup scripts and binaries that make the entire process very simple. To our knowledge proper cold storage techniques are not possible in Grin or Beam. As you can see from some reddit threads, there is little information on the web and the answer is essentially: not possible. It is probably due to the fact that the existing Mimblewimble based coins are not limited in supply and have very high stock to flow ratios today and very few people have had any sort of interest in long term secure storage (that allows for receiving and sending funds to an offline computer).
By necessity, we needed to create a robust cold storage functionality that is available in the full node and wallets to store funds for things like our HODL program and we are releasing our work to the public as well. But we're not the only ones that will need to use cold storage. All exchanges should definitely use cold storage to secure customer funds. It's become painfully obvious that when large enough pools of funds are in a hot wallet, they are hacked. See the binance hack, bitfinex hack, and mt. gox hack. Not an exhaustive list, but clearly you can see how it works from these examples. This begs the question, how are all the exchanges that are listing Grin and other Mimblewimble coins storing them? Are they all in hot wallets? From what we understand the answer to this question is: yes all existing grin coins are currently stored in hot wallets.
This is part of the work we needed to complete before our Q4 launch of mainnet and we are on track. Remember to follow us on twitter, subscribe to our email newsletter, and join our discord to stay informed about MWC.