One question that is typically asked in regards to cryptoviral extortion is the following. How could an extortionist ever expect to receive payment?
e-cash (which may someday be minted off-shore) could provide a safe medium for ransom. Mix networks are also a critical infrastructure for allowing the extortionist to maintain his or her anonymity. Also, the extortionist could seek information that resides on the host machine instead of money. In this case it may be possible for the malware to asymmetrically encrypt the following: cryptographic hash of the desired data concatenated with the randomly generated symmetric key. This would make it so that the symmetric key could not be recovered without revealing the correct hash [YY96a]. See [YY04] for attacks of this nature.
