Method of securing a given original digital file of a batch of a plurality of original digital files (A 1 , A 2 , A 3 ) against forgery or tampering, each original digital file of the batch containing its own digital data (D 1 , D 2 , D 3 ), characterized by comprising the steps of: for each original digital file of the batch, calculating by means of a one-way function an associated digital file signature (x 1 , x 2 , x 3 ) of its digital data; calculating a reference aggregated digital signature (B) corresponding to the batch of original digital files from all the digital file signatures of the original digital files of the batch by means of a one-way accumulator of said digital file signatures, and making available to a user the reference aggregated digital signature; determining a digital file verification key (k i ) corresponding to the digital file signature of said given original digital file by means of a one-way accumulator of all the other digital file signatures used for calculating the reference aggregated digital signature, whereby a candidate digital file signature corresponds to that of an original digital file of the batch only if the reference aggregated digital signature is calculated by means of a one-way function of said candidate digital file signature and corresponding digital file verification key; and including in the given original digital file a digital representation of a machine readable security marking containing a representation of the digital data of the given original digital file and its corresponding digital file verification key, both included into the machine readable security marking via encoding, thereby obtaining a marked original digital file of which digital data are secured against forgery or tampering. for each original digital file of the batch, calculating by means of a one-way function an associated digital file signature (x 1 , x 2 , x 3 ) of its digital data; calculating a reference aggregated digital signature (B) corresponding to the batch of original digital files from all the digital file signatures of the original digital files of the batch by means of a one-way accumulator of said digital file signatures, and making available to a user the reference aggregated digital signature; determining a digital file verification key (k i ) corresponding to the digital file signature of said given original digital file by means of a one-way accumulator of all the other digital file signatures used for calculating the reference aggregated digital signature, whereby a candidate digital file signature corresponds to that of an original digital file of the batch only if the reference aggregated digital signature is calculated by means of a one-way function of said candidate digital file signature and corresponding digital file verification key; and including in the given original digital file a digital representation of a machine readable security marking containing a representation of the digital data of the given original digital file and its corresponding digital file verification key, both included into the machine readable security marking via encoding, thereby obtaining a marked original digital file of which digital data are secured against forgery or tampering. <EOS>