A method for digitally signing an electronic file, characterised by - generating by a server a challenge value comprising a projection parameter, - transferring by the server the challenge value to a client device through a communications channel, - recording biometric data by a biometric data acquisition unit, - by applying a projection utilising the projection parameter, generating reduced biometric data from the biometric data by means of the client device, - generating the hash of the reduced biometric data by means of the client device, - generating the hash of the electronic file by means of the client device, - generating by the client device an evidence record by associating at least the challenge value, the hash of the reduced biometric data, and the hash of the electronic file, - transferring by the client device the evidence record, the electronic file to be signed and the biometric data to the server through the communications channel, - generating by the server reduced biometric verification data from the biometric data applying a projection utilising the projection parameter, - generating by the server a hash of the reduced biometric verification data, - generating by the server a hash of the electronic file, - generating by the server a verification evidence record by associating the challenge value, the hash of the reduced biometric verification data, and the hash of the electronic file, and for comparing it against the evidence record sent by the client device and only continuing the digital signature process if the verification evidence record is identical with the evidence record sent by the client device, - identifying by the server the user of the client device, and defining at least one user data item, - generating by the server a server certificate by associating at least the hash of the electronic file, the at least one user data item, and signature data relating at least to the time of the signature, - signing by the server the server certificate applying the server's private signing key, thereby generating a signed server certificate, - generating by the server a digital signature by associating at least the signed server certificate and the hash of the electronic file, and - associating by the server the digital signature with the electronic file, thereby generating a digitally signed electronic file. - generating by a server a challenge value comprising a projection parameter, - transferring by the server the challenge value to a client device through a communications channel, - recording biometric data by a biometric data acquisition unit, - by applying a projection utilising the projection parameter, generating reduced biometric data from the biometric data by means of the client device, - generating the hash of the reduced biometric data by means of the client device, - generating the hash of the electronic file by means of the client device, - generating by the client device an evidence record by associating at least the challenge value, the hash of the reduced biometric data, and the hash of the electronic file, - transferring by the client device the evidence record, the electronic file to be signed and the biometric data to the server through the communications channel, - generating by the server reduced biometric verification data from the biometric data applying a projection utilising the projection parameter, - generating by the server a hash of the reduced biometric verification data, - generating by the server a hash of the electronic file, - generating by the server a verification evidence record by associating the challenge value, the hash of the reduced biometric verification data, and the hash of the electronic file, and for comparing it against the evidence record sent by the client device and only continuing the digital signature process if the verification evidence record is identical with the evidence record sent by the client device, - identifying by the server the user of the client device, and defining at least one user data item, - generating by the server a server certificate by associating at least the hash of the electronic file, the at least one user data item, and signature data relating at least to the time of the signature, - signing by the server the server certificate applying the server's private signing key, thereby generating a signed server certificate, - generating by the server a digital signature by associating at least the signed server certificate and the hash of the electronic file, and - associating by the server the digital signature with the electronic file, thereby generating a digitally signed electronic file.