The data is still vulnerable to a "rubber hose attack" where the owner is coerced into revealing the hidden keys. Protection against rubber hose attacks might require some form of Shamir secret sharing which splits the keys between diverse phgsical sites.
— Nick Szabo, unedited.
Rubber hose attack is the original name for the wrench attack I was taught on the internet.
Source: Nick Szabo's Smart Contracts: Building Blocks for Digital Markets