Abstract: Method for registering and updating an electronically stored and versioned alpha digital document (A) in a digital document register by storing, for each version, not the document but a public ownership key; a digital document hash value; and a digital document signature. The invention is characterised by the steps a) providing a first document version, defined in a document description language to have a defined rendered graphic representation; b) registering said first version; c) providing a second document version by adding a reversibly added part to said first document version, said second version comprising a second set of metadata; and d) registering said second version, in that said second metadata is embedded in the second version without affecting said graphic representation, in that at least a part of the reversibly added part can be unambiguously generated based on the second metadata, and in that the registering in step d comprises storing a hash of the second metadata.

Abstract: Method for registering an electronically stored digital document (A), comprising the steps of a) providing to an owning party a digital document and a private ownership key, which private ownership key is a private key in an asymmetric cryptographic key pair also comprising a corresponding public ownership key; b) calculating a digital document hash value based upon the document (A); c) the owning party using the private ownership key to calculate a digital document signature of the document (A); d) digitally storing in an electronic digital document register not the document (A), but the document signature as well as the public ownership key and the document hash value. The invention also relates to a system.

Abstract: Method for creating a signal for time-stamping of documents (A), comprising the following steps: a) selecting a digitally stored reference document (D1-D3), which is a digital sample of the current state of a certain reference source at a certain first point in time, where the truthfulness of each reference document can be verified by consulting one or several publically available information sources concerning the historic state of said reference source; b) using the reference document as an input values to a one-way function, and calculating the corresponding output value; c) updating the signal based upon the said output value, so that the said output value (P1-P3) is constituted by or can be determined based upon the value of the signal; and d) repeating from a) using another digitally stored reference document which is a sample of the current state of the same or another reference source at a subsequent point in time.

Abstract: Method for registering an electronically stored digital document (A), comprising the steps of a) providing to an owning party a digital document and a private ownership key, which private ownership key is a private key in an asymmetric cryptographic key pair also comprising a corresponding public ownership key; b) calculating a digital document hash value based upon the document (A); c) the owning party using the private ownership key to calculate a digital document signature of the document (A); d) digitally storing in an electronic digital document register not the document (A), but the document signature as well as the public ownership key and the document hash value. The invention also relates to a system.

Abstract: Method for providing a way to verify the integrity of a document. The invention is characterized in that the method comprises the following steps: a) publishing the document with a visibly embedded piece of information; b) providing a communication channel over which a third party can send a depiction of the published document to the central server; c) accepting said depiction of the published document in the central server, and finding, in the central server and based upon the piece of information, the document; and d) if the document was found in the central server, communicating to the third party that document itself and/or information pertinent to that document. The invention further relate to a system for performing such a method.

Abstract: Method for time-stamping a document the state of which changes over time, comprising the following steps: e) performing a digital sampling of a state of the document at a certain point in time; f) creating a digital signature of the said state, constituted by, comprising or being calculated based upon an output value of a signature one-way function, an input value to which is the sampling; g) embedding the signature into the document, at a point in time which is later than the certain point in time, so that it is possible to read the embedded value from a state of the document at the said later point in time; and h) repeating from a) at the said later point in time; and in that the signature is publically published over at least one publication channel. The invention also relates to a system.

Abstract: Method for creating a signal for time-stamping of documents (A), comprising the following steps: a) selecting a digitally stored reference document (D1-D3), which is a digital sample of the current state of a certain reference source at a certain first point in time, where the truthfulness of each reference document can be verified by consulting one or several publically available information sources concerning the historic state of said reference source; b) using the reference document as an input values to a one-way function, and calculating the corresponding output value; c) updating the signal based upon the said output value, so that the said output value (P1-P3) is constituted by or can be determined based upon the value of the signal; and d) repeating from a) using another digitally stored reference document which is a sample of the current state of the same or another reference source at a subsequent point in time.

Abstract: Method for providing a way to verify the integrity of a document. The invention is characterised in that the method comprises the following steps: a) publishing the document with a visibly embedded piece of information; b) providing a communication channel over which a third party can send a depiction of the published document to the central server; c) accepting said depiction of the published document in the central server, and finding, in the central server and based upon the piece of information, the document; and d) if the document was found in the central server, communicating to the third party that document itself and/or information pertinent to that document. The invention further relate to a system for performing such a method.