Protecting Downloaded Data
The principle proposed for protecting downloaded data is to use digital signature techniques.
In such a scheme, the data is downloaded “in clear” (not encrypted), and a digital signature is appended to the data. The digital signature provides a guaranty of the integrity of the data and of their authenticity. The security mechanisms associated with the digital signature guarantee that there is no way an attacker wanting to modify the downloaded data, and can predict how the signature should be modified to still match the modified data.
Therefore, before law enforcement authorities start using downloaded data, they must verify the integrity of data presented by checking that they match the signature.