The coins will have the private key engraved on the edge of the coin which will be hidden completely by a tamper-proof case. A proprietary cipher system allows verification that the case matches the bitcoin address engraved on the tails side of the coin. No more cheesy holograms. The case will ensure the private key is hidden. All coin cases are signed and numbered by the artist. Case is custom made and is similar to other clear/tamper-proof cases seen with other collectible coins. Bitcoins embedded will be cold stored. You do not have to trust a central authority with these. Bury it in the ground and in 1000 years it will still be good!