Interestingly, the scholar-participants suggested that technological
solutions to the problem [of establishing the authenticity of a digital
object] will probably emerge that would obviate the
need for trusted third parties.
Such solutions may include, for
example, embedding texts, documents, images, and the like with various
warrants (e.g., time stamps, encryption, digital signatures, and
watermarks).
The technologists replied with skepticism, saying that
there is no technological solution that does not itself involve the
transfer of trust to a third party. Encryption -- for example, public
key infrastructure (PKI) -- and digital signatures are simply means of
transferring risk to a trusted third party. Those technological
solutions are as weak or as strong as the trusted third party. To
devise technical solutions to what is, in their view, essentially a
social challenge is to engender an "arms race" among hackers and their
police.
-- Abby Smith "Digital Authenticity in Perspective."
in Authenticity in a Digital Environment,
Council on Library and Information Resources (May 2000)
http://www.clir.org/pubs/reports/pub92/smith.html