This invention provides a means of authenticating digital files without the need for a central trusted authority. A message digest of one or more digital files is calculated, preferably using a cryptographic hash function and all or part of the digest value is implanted into one or more biometric information files produced by the originator of the digital files or a trusted third party. The recipient of the digital files and biometric information files is able to determine all or part of the digest value from the biometric information files, check that this corresponds to the calculated message digest of one or more digital files as well as check the identity of the originator or trusted third party. In further embodiments the biometric information files contain all or part of a digital signature generated by the originator of the digital files or a trusted third party. The invention may be used in many applications including the distribution of public encryption keys.