DE102008041990A1 - Document, method of making and verifying a document, computer program product, data processing system and test system - Google Patents

Abstract

The invention relates to a document with optically recordable document-specific data (202) and an optically detectable representation (204) of a digital signature of the document-specific data.

Description

The The invention relates to a document, in particular a value or security document, a method of making a document, a method of verification a document and related computer program products and Data processing systems and a test system.

Documents are already known from the prior art, which have an RFID chip, by means of which a cryptographic authentication can take place. For example, reference is made to WO 2006/128829 A1 ,

Of the The invention is based on the object, a Document to be created using cryptographic methods is authentic, without any mandatory integrated into the document Chip is required. Furthermore, the invention is based on the object a method of making such a document, a method to review such a document as well corresponding computer program products, a data processing system and to create a testing system.

The The objects underlying the invention are each with the Characteristics of the independent claims solved. Embodiments of the invention are in the dependent Claims specified.

To Embodiments of the invention will be a document with optical recordable document-specific data. The individual documents Data may be on the document in plain text and / or as so-called machine readable zone (MRZ) be printed. The document-specific data can Personal data, d. H. Data regarding the vehicle the document, such as name, address, gender, height, biometric data and / or data relating to the document itself, such as the date of issue, the validity and / or the issuing authority of the document.

The Document also carries an optically detectable representation a digital signature of the document-specific data. The optically detectable representation may be on the document imprinted or by means of another personalization technique be upset. The representation may be a barcode, in particular a 2D barcode, a digital watermark or another machine-readable by means of an optical sensor Act patterns. In particular, it may be in the representation to act by means of Optical Character Recognition (OCR) readable characters. The Representation carries a digital signature of the document-individual Data, for example, using a private key a publisher of the document has been created, or a Protection of authenticity with symmetric methods eg. a MAC.

embodiments of the invention are particularly advantageous because the on the document imprinted optically detectable representation of a digital Signature carries, which for a cryptographic authentication of the document is usable. As for a cryptographic Authentication of the document so no electronic circuit, such as an RFID chip, to be integrated into the document needs, such a document can be reasonably inexpensive getting produced.

To An embodiment of the invention is the document for a value or security document, such as an ID document, d. H. an identity document, such as a Identity card, passport, driver's license or company ID, or a means of payment, such as a banknote, a credit card, or other credentials, such as a Ticket, a bill of lading, a visa or similar. The Document may be paper and / or plastic-based. In particular, the document may be book-like or card-shaped be educated. Furthermore, the document may be a smart card act.

Especially can the document be a so-called visa sticker act, d. H. a visa document, which is to stick in a Passport is provided.

To an embodiment of the invention carries that Document a picture, such as a passport photograph of a wearer of the document. The image can be printed on the document or by means of be applied to another personalization technique. In the Making the document becomes a so-called Image hash generated.

To generate the image hash, use can be made of image-hashing methods which are known from the prior art. Image hashing is understood to mean the conversion of an image into a hash value, whereby two images that are visually identical or almost identical in appearance are very likely to have the same hash value. Such image hashing methods may be eigenvalue based or formed based on a discrete wavelet transform or as hashing via Singular Value Decomposition (SVD) method, cf. For this US 2007 02 39 756 A1 ; "Compact and Robust Image Hashing", Sheng Tang, Jin-Tao Li, and Yong-dong Zhang; "A New Fingerprinting Method for Digital Images", V. Fotopoulos and AN Skodras; "Content-based Image Authentication: Current Status, Issues, and Challenges", Han, Shuihua; Chu, Chao-Hsien; Yang, Shuangyuan; Semantic Computing, 2007. ICSC 2007, International Conference on Volume, Issue, 17-19 Sept. 2007, p. 630-636; "Perceputal Image Hashing Via Feature Points: Performance Evaluation and Tradeoffs", Monga, V .; Evans, BL, Image Processing, IEEE Transactions on, Vol. 15, Issue 11, Nov. 2006, pp. 3452-3465, M. Johnson and K. Ramchandran; "Dither-Based Secure Image Hashing Using Distributed Coding", Proc. IEEE Int. Conf. Image Processing, (Barcelona, Spain), September 2003.

One Image hash is also referred to in the literature as an "image fingerprint".

To Embodiments of the invention will be for the Image of the document generated image hash with the document individual Data combined. This can be done by concatenating the image hash and the document-individual data or by another the image hash and the document-specific data applied reversible Surgery, such as B. by nesting the image hash and the document-individual data or another combination operation respectively. The ones from the image hash and the individual documents Data generated combination is digitally signed and in the optical transformed detectable representation. The document bears in this embodiment, in addition to the individual documents Data an image, wherein the optically detectable representation a signature of a combination of an image hash of this image and of the document-individual data.

A Such embodiment is particularly advantageous, as a result a special level of security against manipulation a document is achieved by swapping the image. If, for example the passport photo is removed from a genuine ID document and replaced by a passport photo of another person, so must one Examining the document will fail as a for the passport photo of the other person's generated image hash from the image hash of the original passport photo is different.

To an embodiment of the invention are for the production the document extracts one or more features from the image. These features may be, for example, geometric features act, such as the position of the eyes, the eye relief, the position of the mouth, etc. in the picture. Such features can be manually, be extracted automatically or fully automatically from the image, for example with the aid of suitable pattern recognition software.

These extracted features are combined with the image hash. The Combining the extracted features with the image hash can lead to Example by a concatenation or another combination operation respectively. The combination of the image hash and the at least one The feature extracted from the image will be referred to hereinafter as "digital Pictorial seal ". The digital image seal can turn combined with the document-specific data. For this combination will then generate the digital signature and in introduced the optically detectable representation. The digital image seal has the advantage over the image hash that it is more robust against inaccuracies in the optical Capture of image data is.

To Embodiments of the invention include the document-individual Data Textual data, such as the data of a MRZ.

To an embodiment of the invention includes the optical detectable representation in addition to the signature and the signed Data itself, d. H. the document-individual data, the image hash, the at least one feature and / or the digital image seal. These Data of the optically detectable representation can with the document review.

In In another aspect, the invention relates to a process for the preparation of a document. According to embodiments of the invention takes place the production of a document by entering individual documents Data in a data processing system, generating a digital Signature for the document-specific data, for example with the help of a private key, the transformation at least the digital signature in an optically detectable representation and the application of the optically detectable representation on a document body. The application of the optical detectable representation can, for example, by printing or by another personalization technique on one of the Layers of the document or on the document surface done. For example, this will personalize a document blank.

To an embodiment of the invention, the documents are individual Data, the image hash, the at least one feature and / or the image seal as well as the digital signature in a predefined data structure brought, for example by a coding. This data structure is then transformed into the optically detectable representation. The data structure can be expressed, for example, by abstract syntax notation 1 (ASN.1).

In In another aspect, the invention relates to a computer program product with executable program instructions for execution a process according to the invention for the preparation of a document. For example, the computer program product serves for controlling a production device for personalization of document blanks.

In In another aspect, the invention relates to a method of verification of a document. According to embodiments of the invention takes place Check with the following steps: Optical Capture of individual document data and a representation a digital signature from the document, inverse transformation the representation to obtain the signature, examination the signature for validity based on that of the document optically recorded individual document data, generation of a Output signal depending on a result of the test the signature.

In In another aspect, the invention relates to a computer program product with executable program instructions for execution an embodiment of an inventive Procedure for verifying a document. For example The computer program product is designed to be of a test system, in particular a tester, to be executed.

In In another aspect, the invention relates to a test system, in particular a tester, for verification a document according to one embodiment a method according to the invention.

in the Further, embodiments of the invention will be referred to explained in more detail on the drawings. Show it:

1 a flow chart of an embodiment of a method according to the invention,

2 a schematic plan view of an embodiment of a document according to the invention,

3 an embodiment of a method according to the invention for checking a document,

4 a flow chart of an embodiment of a method according to the invention for producing a document,

5 a schematic plan view of an embodiment of a document according to the invention,

6 a flow chart of an embodiment of a method according to the invention,

7 a block diagram of an embodiment of a data processing system according to the invention,

8th a block diagram of an embodiment of a tester according to the invention.

elements the following embodiments, which correspond to each other, are each identified by the same reference numerals.

The 1 shows an embodiment of a method for producing a document. In the step 100 Document-specific data is entered into a data processing system. The data processing system may be, for example, a control device of a personalization device for personalizing document blanks. The document-specific data may include, for example, textual data relating to the person of the document bearer and / or the document itself, such as name, place of residence, age, gender, size or date of issue, period of validity or issuing authority. In particular, the document-specific data may be the data of the so-called MRZ of an identity document, in particular according to FIG ISO standard 1073-2: 1976 and ISO 183: 1980 ,

In the step 102 will be in the step 100 digitally signed document-specific data or at least a subset of this document-specific data. This can be done so that a hash value is formed from the document-specific data. This hash value is encrypted using a private key of an asymmetric cryptographic key pair, resulting in the digital signature. The digital signature will then be in the step 104 transformed into an optically detectable representation. Such a representation is understood to mean any form of opto-electronically readable presentation, such as a barcode, in particular a 2D barcode, a digital watermark or a representation that is suitable for OCR recognition.

optional Also, the document-specific data itself becomes the same or another optically readable representation transformed. For example, for this purpose, first the individual documents Data combined with their signature, in particular concatenated, so you get a bitstring. This bit string then becomes transformed into the optically detectable representation, so that these are the individual data of the document as well as their own Signature bears.

In the step 106 the document-specific data and the optically detectable representation are applied to the document, for example by the document-individual data are printed in plain text on the document and in the step 104 generated representation is also printed on the document. The application of the data and the representation in the step 106 can be done using per se known personalization techniques, such as printing technology, by laser personalization or the like.

The 2 shows an embodiment of a document according to the invention 200 , which according to the embodiment of the method of 1 can be produced. The document 200 has a first area 202 who carries individual document data, such as textual data. The document 200 also has an area 204 carrying the optically detectable representation formed here as a 2D barcode. This embodiment of the document 200 is particularly beneficial for applications where the document needs to be of a particularly low price, such as tickets or other credentials. In particular, the document needs 200 in this embodiment, have no image of the wearer of the document.

The 3 shows an embodiment of a method for verifying the authenticity of the document 200 ,

In the step 300 will be the textual data from the field 202 and the representation from the field 204 optically recorded. This can be done with the help of a scanner, a CCD camera or another optical sensor. For example, the entire front of the document 200 captured in the area 202 and 204 automatically detect. For example, the position of the areas 202 and 204 in the document 200 be predefined.

In step 302 becomes the barcode of the area 204 retransformed, so that the previously in the step 104 retrieves data transformed into the representation, ie, for example, the textual data contained in the step 100 have been entered, as well as their signature (see. 1 ).

In the step 304 it is checked whether the signature is valid. This can be done so that from the textual data of the representation according to the same hash method, which in the step 102 has been applied, a hash value is formed. The signature is decrypted using the public key belonging to the cryptographic key pair, so that the one in the step 102 returns the generated hash value. If both hash values match, the signature is valid.

Thereupon, in the step 308 Check if the out of the area 202 recorded textual data with the textual data obtained by reverse transformation from the barcode. If this is the case, in the step 310 generates a signal indicating the authenticity of the document. If, on the other hand, the signature is not valid, then in the step 306 generates a signal indicating that the document is forged. Likewise, from the step 308 to the step 306 gone if the textual data obtained by inverse transformation of the optical representation does not coincide with those from the area 202 collected textual data.

Alternatively, it is also possible to proceed in such a way that for checking the signature in the step 304 those from the field 202 captured textual data. From the textual data of the area 202 then the hash value is generated, which is compared with the hash value obtained from the signature by decryption with the public key. If the two hash values match, the signature is again valid. In this embodiment, the step 308 This is because the signature can only be valid if not only the private key used for the signature matches the public key used for the verification, but also the one from the area 202 captured textual data matches those in the step 102 originally digitally signed.

The 4 shows a further embodiment of a method according to the invention for producing a document. In this embodiment, a document is to be produced which has an image, such as a facial image of the wearer of the document. In the step 400 The image data is input to a data processing system. For example, the image is a digital photograph so that the image data is originally in a digital format. Alternatively, the photo is in a physical form, such as a paper print or imprint. In this case, the photograph is digitized with an optical sensor to capture the image data.

In the step 402 an image hash of the image data is generated using an image hashing process. Optionally, one or more features may additionally be extracted from the image data. These may be geometric features, such as the position of the eyes, the distance between the eyes, the position of the mouth. These features are added to the image hash For example, by appending a corresponding bit string to the image hash, ie concatenated is. In this way, a so-called image seal is created, which is particularly meaningful with respect to the image data, and thus has a high degree of robustness against inaccuracies in the subsequent optical detection of the image data from the document.

In the step 404 Document-specific data, such as textual data, are entered into the data processing system. In the step 406 The textual data and the image hash are combined. This can be done in such a way that a bit string representing the textual data and a bit string representing the image hash are concatenated or interleaved, for example by block-by-block data blocks of the textual data following data blocks of the image hash. In the event that from the image data in the step 402 One or more features have been extracted which have been combined with the image hash to the image seal, as done in the step 406 a combination of the textual data with the image seal instead of just the image hash.

In the step 408 will be in the step 406 combined data digitally signed. For example, for this purpose, a hash value is generated from the combination of the data, which is encrypted using a private key of a cryptographic key pair, from which the signature results.

In the step 410 The textual data, the image hash or the image seal and the signature are transformed into an optical representation, such as a 2D barcode. Before the transformation, these data, ie the textual data, the image hash or the image seal, and the signature can be converted into a predefined data structure, for example according to ASN. 1. This predefined data structure is then placed in the optical representation to transform the data.

In the step 412 For example, the image data, textual data, and visual representation are applied to the document, such as by printing or other personalization technique, such as laser personalization.

The 5 shows a corresponding embodiment of a document 200 which according to the method according to 4 has been produced. The document 200 has an area 206 who wears an embodiment of the image which is the one in the step 400 entered or captured image data corresponds. This may be, for example, a facial image, in particular a passport photograph, of the document's wearer 200 act. The document 200 Furthermore, a so-called MRZ 208 exhibit. Like the area 202 so does the MRZ 208 textual data. At least part of this textual data may be in the step 406 into the combination with the image hash or the seal of approval.

The 6 shows a flowchart of a method for verifying the authenticity of such a document 200 , In the step 500 becomes the document 200 detected by an optical sensor, such as an optical scanner or a CCD camera. Through the optical detection of the area 206 the image data of the image located there are captured. Out of the area 204 the optical representation, ie for example the 2D barcode, is detected. From the fields 202 and or 208 For example, the textual data is captured by OCR.

In the step 502 an image hash is generated from the image data. In the step 504 the optical representation is transformed back, so that in the step 410 (see. 4 ) transformation is reversed. As a result, the data processing system executing the method receives the textual data originally introduced into the optical representation, the image hash and the signature.

In an embodiment with an image seal, in the step 502 extracts the one or more features from the image data to obtain the image seal therefrom.

In the step 506 it is checked whether the by the inverse transformation in the step 504 obtained signature is valid. This uses a public key that belongs to the same asymmetric key pair as the one in the step 408 used private keys. If the signature is not valid, then in the step 508 a signal is issued, after which the document is forged.

If the signature is valid, on the other hand, in the step 510 checked if the in the step 510 textual data collected by the document through OCR in the step 504 match textual data obtained by backtransforming the optical representation. If this is not the case, in the step 508 again, that the document is forged.

In the opposite case, in the step 512 checked if the image hash, which in the step 502 has been generated from the optically acquired image data, with the reverse transformation in the step 504 obtained image hash matches. If this is not the case, then in the step 508 issued that the document is fake; in the opposite case, in the step 514 issued that the document is genuine. In an embodiment with image seal is in the step 512 checked if that in the step 502 generated image seal with the by inverse transformation in the step 504 obtained image seal matches.

The 7 shows a data processing system 210 for producing a document 200 , The data processing system 210 has a generator 212 for a picture seal. The generator 212 has a program module 214 which implements an image hashing method. For example, the image hashing method is based on a principal component analysis.

Furthermore, the generator has 212 a program module 216 which implements a feature extractor. The feature extractor is based on an image processing method for extracting one or more geometric features from the image. The image data can be stored in digital form in the generator 212 be entered. If the image is from a digital image source, the image data provided by the digital image source can be used immediately. Alternatively, the image may for example be in the form of an imprint from which the image data is obtained by scanning.

If the image data comes from an analog image source, the image data may be input to the generator prior to input 212 wherein the filter simulates the change in the image represented by the image data when it is applied to the document and / or during the later optical detection of the image data from the image. For example, the image data is normalized by the filter. The image data or the normalized image data are then in the generator 212 entered through the program module 214 an image hash of the image data is generated and with the help of the program module 216 one or more features are extracted from the image data. The image hash and the at least one feature are then combined together, for example, by concatenating the corresponding bit strings, so that at the output of the generator 212 the image seal is output.

The data processing system 210 also has a MRZ generator 218 for generating the MRZ from in the data processing system 210 entered textual data, in particular personal data relating to the carrier of the document 200 may include.

The data processing system 210 also has a concatenator 220 for the concatenation of the image seal and the MRZ. For example, the image seal and the MRZ are from the generator 212 or from the MRZ generator 218 each output in the form of a bit string. Through the concatenator 220 These two bit strings are linked together. This results in a combined bit string.

The data processing system 210 also has a signer 222 for generating a digital signature for that of the concatenator 220 output combined bit string. For this the signer has 222 Access to a private key belonging to the data processing system 210 or an operator of this data processing system 210 assigned.

The data processing system 210 also has an encoder 224 , The encoder 224 The purpose of this is to first bring the data that is to be incorporated into the optically detectable representation into a predefined data structure. Such a data structure can be done with the help of ASN. 1 be specified. For example, the encoder brings 224 that of the signer 222 generated digital signature and that of the generator 212 supplied image seal in the predefined data structure.

The data processing system 210 also has a generator 226 for the optically detectable representation. The generator 226 gets from the encoder 224 the predefined data structure, which includes the digital signature and the image seal. The generator generates for this data structure 226 an optically detectable representation, such as a 2D barcode.

The data processing system 210 also has a generator 228 for a print file. The generator 228 receives the MRZ from the MRZ generator 218 as well as the optically detectable representation of the generator 226 and creates a print file from it. In addition, additional data can be included in the generation of the print file, such as the image data and other data. From the generator 228 becomes a printer 230 or another personalization device driven to a document blank 232 to print, so you have the personalized document 200 receives.

The 8th shows a block diagram of a test system for checking the authenticity of the document 200 , The test system can, for example, as a tester 234 be formed, for a stationary or mobile use. The tester 234 can be attached to an optical sensor 236 be connectable or include such.

The tester 234 has a transformer back 238 for inverse transformation of the optical representation to that of the generator 226 (see. 7 ) undo transformation. Furthermore, the tester has 234 a decoder 240 which serves that of the encoder 224 undo the coding that has been carried out. The decoder 240 thus serves to recover the data contained in the predefined data structure.

The decoder 240 is with a concatenator 220 connected, which is designed to perform a concatenation, as well as for the concatenator 220 of the 7 the case is. The tester 234 also includes an OCR module 242 , which also with the concatenator 220 connected is. An outlet of the concatenator 220 and the decoder 240 are with a signature verifier 244 connected. It has access to a public key belonging to the same cryptographic key pair as the private key used by the signer 222 is used.

The tester 234 also has a generator 212 with program modules 214 and 216 which in principle have the same operation as the generator 212 with these program modules in the embodiment of the 7 , An output of the generator 212 is with a comparator 246 which is also connected to an output of the decoder 240 connected is.

Furthermore, the tester has 234 an evaluation module 248 for the evaluation of the comparator 246 and the signature verifier 244 supplied signals.

The tester 234 also has an edition 250 to output a result of the evaluation. At the issue 250 it may, for example, be a display device, an acoustic output and / or a machine interface. For example, about the output 250 a turnstile will be automatically released unless the document 200 from the tester 234 has been recognized as genuine.

The document will be put into operation first 200 with the help of the optical sensor 236 optically recorded. Those from the area 204 (See embodiment of the 5 ) is converted into the inverse transformer 238 entered and transformed back there. The inverse transformer 238 then gives to the decoder 240 the data structure. This is done by the decoder 240 decoded. The image seal included in the data structure is provided by the decoder 240 in the concatenator 220 entered.

The of the optical sensor 236 out of the area 208 captured data will be in the OCR module 242 entered to perform optical character recognition. This will remove the MRZ from the document 200 read. The MRZ is powered by the OCR module 242 in the concatenator 220 entered. The concatenator 220 then concatenate the MRZ and the decoder 240 delivered pictorial seal, as well as for the concatenator 220 in the embodiment of the 7 the case is.

The concatenated bit string resulting from the concatenation of the MRZ and the image seal is provided by the concatenator 220 in the signature verifier 244 entered. Furthermore, the signature verifier obtains the digital signature obtained from the data structure from the decoder 240 , The signature verifier then forms a hash value from the concatenated bit string and decrypts the digital signature using the public key. The hash value resulting from this decryption must match the hash value obtained from the concatenated bit string for the signature to be recognized as valid. The signature verifier 244 gives a signal to the evaluation module 248 off, which indicates whether the signature is valid or not.

In the generator 212 Further, those of the optical sensor 236 out of the area 206 input captured image data. The generator 212 creates an image seal from the image data, as well as for the generator 212 in the embodiment of the 7 the case is. The generator 212 gives the image seal to the comparator 246 out.

The decoder 240 also gives the image seal obtained from the data structure to the comparator 246 out. The comparator 246 compares the two pictorial seals with each other. If the image seals match, it follows that from the document 200 captured image has not been replaced by another, what the comparator 246 with a first signal to the evaluation module 248 signaled.

In the opposite case, the comparator gives 246 a second signal. The evaluation module 248 then generates a first output signal indicating the authenticity of the document 200 signals when it comes from the comparator 246 receives the first signal and if the signature verifier 244 the validity of the signature is signaled.

If the evaluation module 248 by contrast, from the comparator 246 receives the second signal and / or is signaled by the signature verifier that the signature is not valid, so generates the evaluation module 248 a second output signal to indicate that the document 200 is fake. The first and second output signals are then output 250 from the tester 234 output.

According to an alternative embodiment, the image hash is used directly instead of the image seal, both from the data processing system 210 as well as from the tester 234 , However, the use of the image seal is advantageous over the use of only the image hash, as this renders the robustness of the test against wear of the document 200 , Soiling or scratches of the document surface, inaccuracies in the optical detection or the like is increased.

200

document

202

Area

204

Area

206

Area

208

MRZ

210

Data processing system

212

generator

214

program module

216

program module

218

MRZ generator

220

Konkatenator

222

signer

224

encoder

226

generator

228

generator

230

printer

232

documents blank

234

tester

236

optical sensor

238

inverse transformation

240

decoder

242

OZR module

244

signature verification

246

comparator

248

evaluation module

250

output

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• WO 2006/128829 A1 [0002]
• US 20070239756 A1 [0011]

Cited non-patent literature

• - ISO Standard 1073-2: 1976 [0035]
• - ISO 183: 1980 [0035]

Claims (20)

Document with optically recordable document-specific data ( 202 ) and an optically detectable representation ( 204 ) of a digital signature of the document-individual data. The document of claim 1, wherein the optical Representation around a barcode, especially a 2D barcode, or a digital watermark or where the optical Representation formed for an optical character recognition is. A document according to claim 1 or 2, wherein the document is an image ( 206 ), wherein the digital signature is a signature of a combination of an image hash of the image and the document-individual data. Document according to claim 1, 2 or 3, wherein the document carries an image, and wherein the digital signature a signature of a combination of an image hash of the image, of at least one feature extracted from the image and the individual document Data is about. Document according to claim 4, wherein the feature is a geometric feature. Document according to one of the preceding claims, the document-specific data comprising the data of a machine-readable line ( 208 ). Document according to one of the preceding claims, wherein the optically detectable representation of the document individual Data and / or an image hash of an image of the document and / or at least one feature extracted from an image of the document includes. Method of producing a document ( 200 ) with the following steps: - input of document-individual data, - generation of a digital signature of the document-individual data, - transformation of the digital signature into an optically detectable representation, - optically detectable application of the document-individual data and the representation on a document body. Process according to claim 8, with the following further steps: - Capture of image data on the Document applied or to be applied, - Generation an image hash of the image from the image data, - Generation a combination of the image hash and the document-individual Dates, where the digital signature is a signature the combination of the image hash with the document-individual data is. The method of claim 9, wherein from the image data At least one feature is extracted, the feature with the Image hash and the document-individual data is combined, where the signature is a signature from the combination the image hash, the at least one feature and the document-individual Data is about. The method of claim 10, wherein the at least one feature around a geometric feature of the image is. Method according to one of the preceding claims 8 to 11, wherein the document-individual data, the image hash, the at least one feature and / or the digital signature before the Transformation into a predefined data structure, wherein the data structure transforms into the representation becomes. Computer program product with executable Program instructions for carrying out a method according to one of the preceding claims 8 to 12. Data processing system comprising: - means ( 222 ) for generating a digital signature of individual document data, means ( 226 ) for transforming the digital signature into an optically detectable representation, 228 ) for optically recordable application of the document-individual data and the representation on a document body ( 232 ). Procedure for verifying a document ( 200 ) comprising the following steps: - optical recording of individual document data and a representation of a digital signature of the document, - backward transformation of the representation to obtain the signature, - verification of the signature for validity based on the document individual data optically acquired by the document, - generation of an output signal depending on a result of the verification of the signature. The method of claim 15, wherein the document is an image ( 206 ), wherein the representation includes a first image hash of the image, and wherein the signature is a signature of a combination of the first image hash and the doku with the following further steps: - optical capture of the image from the document, - generation of a second image hash from the optically acquired image data of the image, - checking whether the first and the second image hash match. The method of claim 16, wherein the representation includes a first feature, wherein the digital signature a signature of a combination of the first image hash, the first feature and the document-individual data, with the optically captured image data, a second feature is extracted, and wherein It is checked whether the first and second features match. Method according to one of the preceding claims 15 to 17, wherein by reverse transformation of the optical Representation generates a predefined data structure which the document-specific data, the first image hash, includes the first feature and / or the digital signature. Computer program product with executable Program instructions for carrying out a method according to one of the preceding claims 15 to 18. Test system for checking a document ( 200 ) with: - means ( 236 ) for optically capturing document-individual data and a representation of a digital signature of the document, - means ( 238 ) for the back transformation of the representation to obtain the signature, - means ( 244 ) to verify the signature for validity on the basis of the document - specific data optically recorded by the document, 248 ) for generating an output signal in response to a result of the verification of the signature.