DE102008053219A1 - Character string e.g. transaction authentication number, transmission method for online bank accounts, involves transmitting information to server, and reconstructing character string, inputted by client, by server - Google Patents

Abstract

The method involves producing a punch card or a sheet according to a process of cardano coding by a server, and generating an image with blocks of characters by the server. The image is displayed at clients, and the card or sheet and a screen are superimposed by the clients. Selectably labeled characters are visible as pushbuttons for the clients, and a string of characters is input by the clients via mouse clicks on the pushbuttons. Information, which has clicked on the pushbutton, is transmitted to the server, and the character string inputted by the client is reconstructed by the server. The punch card or sheet is made of plastic or paper. Independent claims are also included for the following: (1) a punch card or sheet for implementing a method for tap-proof transmission of a character string from a client to a server (2) a computer program product comprising instructions to perform a method for tap-proof transmission of a character string from a client to a server.

Description

The The present invention relates to a method for monitoring and tamper-proof encryption for Online accounts, in particular for online bank accounts, by means of Cardano encryption.

The Listening and Tampering Security of Online Accounts - Especially that of online bank accounts - is getting bigger by the Expecting quantity and harmfulness of malware (i.e., viruses, etc.) on the PC's of bank customers. Method, which both the listening to the PIN and a so-called To safely prevent man-in-the-middle attacks are technically complex and need special hardware and software on the from Bank customers used PC.

The The privacy of the PIN is obvious in the PIN / TAN procedure: the malware on the client's computer is secretly observed Enter the PIN the keyboard input. Later the intercepted PIN secretly passed through computer network to another computer. From there, the user can access the account at least by reading become. Procedures where the PIN with mouse clicks on the screen are also not tap-proof: the Malware simultaneously stops screen and mouse movement.

method like HBCI-2 for bank accounts (with external number field to the Entering the PIN) or the clock-controlled security token for Corporate accounts protect the PIN from eavesdropping but elaborate in manufacture and use.

Of the sees man-in-the-middle attack on an online account Banker X wants 50 euros transfer to Y's account. He fills the corresponding one Online form and send it off. The malware on the machine intercepts this transfer order before he sent to the bank, converts him into a transfer from 5000 euros to Z, and sends this manipulated transfer order to the bank. The demand of the bank to X for a TAN for the transfer order of 5000 Euro to Z will be provided by the Malware in the reverse direction also intercepted, and it Bank client X is prompted by the bank's demand on the screen a TAN for a transfer order of 50 Euro to Y reflected. Unknowingly X confirms with a TAN this pretended order, and the malware sends out the X entered TAN to the bank to continue the fraudulent transfer order from 5000 Euro to Z to confirm.

The PIN / TAN, PIN / iTAN, HBCI-1, HBCI-2, and Security Token procedures not safe from man-in-the-middle attack. The encryption of the connection (eg SSL) also protects not sure, because the malware can be down even before the connection encryption turn on and the manipulations even before the connection encryption (or in the other direction: after the connection decryption) carry out.

Method, that protect against man-in-the-middle attacks, are the ones that have both a numeric keypad and a display attach outside of the client computer, such. B. HBCI-3. However, due to the physically existing cable connection between this extra hardware and the client's computer still a residual risk that malware on the client's computer the actions spied on the extra hardware. One more way is to get the transfer data by SMS from the bank to confirm ("mTANs") This solution is that a cell phone must be present and that the reception of the SMS may take a while. Furthermore It is only a matter of time before mobile phones are affected by malware and thus this possibility is also uncertain.

The patents EP1472584B1 . US2005 / 0219149A1 and DE-10-2007-018802.3 , 2007 propose to ensure the security of online accounts through visual cryptography. In the essay ( Naor &Pinka's"Visual Authentication and Identification", CRYPTO, Springer Verlag, 1997, p. 322-336 ) the application of visual cryptography for the security of smart cards is proposed and analyzed. In this application, Cardano encryption is used instead of Visual Cryptography for the same purpose.

Some The known encryption methods are based on the 450 years old method of Cardano encryption: one Transmitter A wants the receiver B inaudible Send messages. For that purpose the transmitter produces a map with punched holes at random Positions and send a copy of it to the recipient B. Now A can send an inaudible message to B, by taking a card of the same size that Card with the holes on it, in the holes the Letter of his message writes, and then the card with the Remove holes and randomize the rest of the unperforated card filled up with letters. He sends this card to B. B Place the copy of the punched card on the received card and can read the message. Without the punched card as a key but no one can use the letters of the unperforated card Make sense.

The patent US20060020559A1 describes an encryption method for online accounts based on the Cardano principle described above (the name Cardano is not mentioned). In this method, punched paper cards are placed on the screen to show secret information to the user.

The The object of the present invention is to provide a secure encryption method to provide for online accounts, including sending a inaudible and thus not manipulatable message allowed by the client to the server.

To solve this problem, the method of Cardano encryption is used, according to the invention, the new principle "card-on-screen" is used: The hole pattern is punched out on a card or printed on a transparent film, the other is displayed on the screen The slide on the screen is therefore the original information for the user to see It is crucial that no malware on the user's computer or in the computer network can recognize the original information: there is no possibility for malware, the slide on the screen to "scan". 1 shows the situation: the blocks of numbers on the screen and the slide of the user superimposed reveal a bar of numbers with random numbers. For malware on the computer or in the computer network, there is no way to recognize the interchange of 10 digits.

In order to the printed on the film hole pattern or the punched card with the blocks of characters displayed on the screen can be placed on top of each other, the film is fixed on the screen. For this purpose, individual slides can provided with adhesive tape on one or more edges become. In this case, the slides can be analogous to sticky notes stacked in a notepad on top of each other and through the Adhesive strips are kept together.

It is an example of the invention according to the following Method for the tap-proof handling of an online account described. This example will output a text with n characters an alphabet consisting of m characters with n mouse-clicks absolutely secure from a client through a computer network to a server. Here and below will be under Alphabet, as usual in computer science, a finite amount understood by signs. In this sense, for example, the amount the numbers 0, ..., 9 an alphabet with 10 characters.

First For each client, the server creates a set of sub-secret images, which he names and stores (eg numbers) and saves. Then prints He prints these images on punched cards or transparencies in addition their respective name (number) visible on it, and sends these punched cards or foils physically, so z. B. by mail, to the client. At the beginning all of them have partial secrets pictures the status "unconsumed", later used in "used up" can change. This status is managed by the server.

Of the Client X now has these punch cards and wants to give the server a secret Send message of n characters (example: he wants to send him an 8-digit bank code). To do this, he steps on his computer online via the computer network Connects to the server and presents itself to the server as a client X before.

Of the Server takes note of this and then creates an original image for transmission of n characters from an alphabet with m characters in the following way. On the picture are at least n + m - 1 buttons generated. The buttons serve as surfaces to later click with the mouse and overlap not. The buttons carry labels. each Character of the alphabet appears as a caption on at least one of the buttons. In addition there are n - 1 Buttons, each for a reference to a sign that has already occurred. Ideally these references are numbered 1 to n - 1 labeled (if the numbers themselves are part of the alphabet are, these numbers are specially marked, z. B. by a preceded P for "position"). The assignment Labels and buttons become random generated. The server remembers this random assignment.

A special case occurs when the text to be transmitted is guaranteed to have no character repetition (a plausible example: only PINs consisting of the digits 0, ..., 9 are permitted, in which no digits occur multiple times). In this case, the buttons with the references to the previous position can be omitted, and one button is enough for each character of the alphabet. 1 shows an image with a randomly generated array of buttons for the numbers 0, ..., 9.

After this The server has created such an original image, he takes one more unused saved part secret image for the Clients X, makes from these two pictures according to the procedure of Visual cryptography a second (electronic) partial secrecy image, which he then he through the computer network online on the screen of the client. Also the name (number) of the stored Partial secret image sent to the client's screen. The saved partial secret image gets the status of the server "consumed".

Client X sees the partial secret image and its name (number) on the screen. He puts the slide with the same name (number) on the screen, specifically on the partial secret picture on the screen. Because the two partial secret images were generated by the method of visual cryptography, client X can see the original image.

In In practice, the two pictures are not the same size. The The image on the screen must therefore be adjusted by the client (eg stretched) can be, best by mouse.

Of the Client sees the original image with its buttons and their labels. He can now his secret text via Enter mouse clicks according to the following rules.

One Text with n or fewer characters becomes characters as follows entered for characters. For every character, that has not occurred before, the button, on which the sign stands, clicked. If a sign has already occurred, the largest position in the text is determined the sign already stood: the button, its caption is a reference to this position, is clicked.

To These simple rules guarantee that every button only once is clicked on. The software on the client machine can because of this, potentially supporting the user and all ever clicked buttons specifically show z. For example, in the partial secrecy image on the screen, all pixels of the clicked Invert button. That's what the user sees Buttons he should not click, the security against eavesdropping will not be affected.

A further possible support for the user offer - as he knows it from the bank machine - one Correction button and a progress bar labeled with "asterisks" indicates how many characters have already been entered.

At the server gets the information about the clicked buttons and their order sent, z. B. by changing the pixel positions n mouse clicks are transmitted relatively in the sub-secret image, or any other unique description of the clicked buttons becomes.

Because each button is clicked at most once and the Caption of buttons selected randomly Malware may be on the client's computer or in the computer network no information about the transmitted text open up: the malware would have to be launched Spying on film, which is not possible.

The Information sent to the server can be there afterwards be decrypted: the server knows the original image and know which labels the buttons clicked on to have. So he can from the transmitted n descriptions of buttons the message entered by the client reconstruct from n characters. The message was therefore tap-proof transferred from the client to the server.

Of the Advantage of the method described is thus that a Online account safe from listening to the PIN and secure protected from the man-in-the-middle attack. Of the Reason lies in the fact that malware (on the computer of the bank customer or in the computer network) the aufzulegende punch card / foil does not know and definitely can not spy (a "scan" the punched card / slide via screen is absurd!).

A Variant of Cardano encryption is in place Punching holes in paper and so on after overlaying letters highlight, mark on a slide surfaces, so that after superimposing letters thereby highlighted be that they lie on these marked areas. With this principle also foil and screen can be exchanged be, d. H. on the screen, surfaces are highlighted and on the slide are the letters. This variant is supposed to be inverted Cardano encryption are called.

In show the drawings:

1 : Principle of Cardano encryption: neither the card with the holes nor the image with the bush blocks have information individually, but superimposed they show an interchanging of the numbers 0 to 9. The client can now z. B. enter his PIN with mouse clicks.

2 : Counterfeit-proof transfer: If the lottery card is placed on the screen, the bank transfer data available to the bank is visible. The client confirms the transfer by clicking on the blocks that display hyphens.

3 : Principle of the inverted Cardano encryption: neither the map with the surfaces nor the image with the numbers have information individually, but superimposed they show an interchanging of the numbers 0 to 9. The client can now z. B. enter his PIN with mouse clicks.

embodiment

The above procedure for sending secret messages between server and client is applied to the special case of Onli ne-banking ( 1 and 2 ). The method prevents PIN listening and man-in-the-middle attack.

Of the Bank server generates for the bank customer X a lot of Punch cards, number them, save them, and send them to Bank customers by mail (ie similar to TAN lists be sent). In addition, the customer will like the PIN / TAN procedure, it is assumed that that no digit occurs twice in the PIN (the number of possibilities is still enough to make it futile to guess the PIN)

If the customer X has received the slides and his PIN, he can start online banking. To log in, he goes to the web page of the bank and there gives his account number. at. The account no. will be sent to the bank server. The bank server now checks the authenticity of X as follows:
The bank server generates a random interchange of the digits 0, ..., 9. These characters are written at positions in the blocks corresponding to the holes on the punched card. This is sent to the bank customer X in his browser window, including the number of the stored partial secret image.

Of the Bank customer sees the picture and its number and places its corresponding Punched card / foil on it. He can do this with an exchange of digits 0 to 9 recognize. Suppose his PIN is 41629. Then he clicks So one after the other blocks, the numbers 4, 1, 6, 2, 9 show. The numbers of the clicked blocks become sent to the server. Because the bank server remembered the exchange now he can directly conclude that by the mouse clicks the number sequence 41629 was entered. He compares this number sequence with the PIN for bank customer X (which, of course, also saved is). If that was the correct PIN, the bank customer gets X access to the account.

listening end Malware (on the computer used by bank customer X or on the Internet) has no chance to listen to the PIN: the positions of mouse clicks and the block numbers sent to the server have no meaning as long as the interchanging of the numbers is not known. This knows but only the bank server and the one on the browser the corresponding one Can hang up film.

bank customer X gets so with the knowledge of the PIN and the physical possession the slide access to his bank account. Only one of them is enough not from. The procedure thus protects the PIN twice: First, it is not audible, and if someone does other way, he needs the right one Slide: without it he does not come into the account.

The Cardano process can also thwart a man-in-the-middle attack: the bank transfer data pending on the bank are represented by the punch card / foil placed on the screen, see 2 , The customer confirms this oversight by mouse clicks on certain blocks, in the case shown by clicking on the blocks with hyphens. Thus, if the bank server receives the correct clicks, the information about the actual transfer has reached the bank customer X, and no pre-mirrored information. A man-in-the-middle attack is thus repulsed with this method.

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

• - EP 1472584 B1 [0008]
• US 2005/0219149 A1 [0008]
• - DE 10-2007-018802 [0008]
• US 20060020559 A1 [0010]

Cited non-patent literature

• - Naor &Pinka's"Visual Authentication and Identification", CRYPTO, Springer Verlag, 1997, pp. 322-336 [0008]

Claims (16)

Method for secure transmission a string of characters from a client through a computer network to one Server, characterized by the following steps: a) the Generating a punched card or a film according to the Method of cardano encryption by the server, b) generating an image with blocks of characters the server, c) displaying the image from b) at the client, d) the overlapping of the punched card or foil and the Screen by the client, with the clickable labeled Characters visible as buttons for the client become, e) the input of a series of n characters by the client via mouse clicks on the labeled buttons, f) the transmission of information about which buttons the client clicked in which order, to the server, G) the reconstruction of the character string entered by the client the server. Method according to one of the preceding claims, characterized in that the punched card or film made of plastic or paper. Method according to one of the preceding claims, characterized in that the punched card or film made of plastic or paper is printed with black or colored paint. Method according to one of the preceding claims, characterized in that the punched card or film made of plastic or paper is punched out. Method according to one of the preceding claims, characterized in that the characters in the picture are numbers, letters and / or special characters. Method according to one of the preceding claims, characterized in that the image with the clickable and with Labeled buttons represent a number field, where the number is between 0 and 9 respectively the individual buttons assigned. Method according to one of the preceding claims, characterized in that the labels on the buttons in the picture a reference to the position of the button to be clicked include. Method according to one of the preceding claims, characterized in that the number of buttons n + m - 1, where m is the number of all for is the input of available characters. Method according to one of the preceding claims, characterized in that the character string is a password PIN, a TAN or similar is. Computer program product for execution of the method according to any one of claims 1 to 9, when the Computer program is running on a processor. Punch card or film for carrying out the method according to one of claims 1 to 12, characterized that they have a partial secret image according to the procedure The Visual Cryptography includes and for fixing on the Screen is provided with at least one adhesive strip. Punch card or film according to claim 11, characterized that it consists of a transparent material. Punch card or film according to one of the claims 11 to 12, characterized in that it is printed with color. Punch card or film according to one of the claims 11 to 13, characterized in that they are black or colored Color is printed. Punch card or film according to one of the claims 11 to 14, characterized in that it is punched out. Use of the method, the computer program product or the film according to any one of the preceding claims with online accounts.