For real cold storage, do not rely on paper or USB keys. A piece of paper, a USB key - is this really the way I should keep my crypto assets? Well, if it is just for myself, and the value of crypto coins does not exceed a few hundred bucks, then storing my private key that way might be good enough. However, if I am holding a hundred million in crypto currency, be it for my customers or myself, I obviously need a more reliable solution.
This solution does exist. It is an HSM, a hardware security module in the form of a network appliance. This box generates safe and sound public/private key pairs, holds them in a tamper-controlled enclosure, and controls access to them. It should be operated in clusters across sites to provide geo-redundancy. Fiat currency systems like that for the Swiss Franc are using appliance HSM to safeguard their transactions with public/private keys (PKI). In the Swiss interbank clearing and settlement system, daily transactions of over 100 Billion Swiss Francs are secured by Securosys HSMs.
The very same HSM can be used to securely store crypto assets - something we already started implementing with our partners in the crypto finance field. Cold storage of crypto coins on Securosys Primus HSMs is scalable and more secure than paper printouts or USB keys. Securosys is committed to expanding the functionality of its Primus HSM to even better interact and protect crypto currencies, assets, and blockchains. If you would like to learn more about Securosys or on how to use our HSM, pleasecontact us.