Electronic signing apparatus and methods

• US 7,581,105 B2
• Filed: 12/16/2003
• Issued: 08/25/2009
• Est. Priority Date: 12/16/2003
• Status: Active Grant

• Current Assignee: SAP SE
• Original Assignee: SAP AG (SAP SE)
• Inventors: Dietl, Josef
• Primary Examiner(s): Lipman; Jacob
• Application Number:
  US10/738,660
• Publication Number:
  US 20050132195A1
• Time in Patent Office: 2,079 Days
• Field of Search: 713/176
• US Class Current: 713/176
• CPC Class Codes: G06F 21/64 Protecting data integrity, e.g. using checksums, certificates or signatures
• CPC Class Codes: H04L 2209/608 Watermarking
• CPC Class Codes: H04L 9/3231 Biological data, e.g. fingerprint, voice or retina network architectures or network communication protocols for supporting authentication of entities using biometrical features in a packet data network H04L63/0861
• CPC Class Codes: H04L 9/3236 using cryptographic hash functions
• CPC Class Codes: H04L 9/3247 involving digital signatures

Abstract

Methods, apparatus, including computer program products, and systems implement and use techniques relating to electronic signatures. In one implementation, a one-way hash is calculated for an electronic document and a digital watermark representing the one-way hash is embedded in a signature document. Based on a user input, the signature document having the embedded digital watermark is altered, and the electronic document is associated with the signature document. The electronic document and the signature document together comprise a signed electronic document. The user input can include biometric information, such as a handwritten signature or a voice recording. For additional security, the one-way hash can be encrypted before a representation of the hash is embedded in the signature document.

Claims

1. A method comprising:

receiving at a signing device an electronic document provided by a source device;

preventing alterations to the electronic document presented to a user using the signing device;

identifying a signature document including a digital image embedded with a digital watermark, wherein the digital watermark is an image that represents a watermark and overlays at a least a portion of the digital image and embeds in the signature document, independent of any private key of a user, a one-way hash calculated using the electronic document;

in connection with presenting the signature document including the watermark image applied to the digital image, receiving an electronic handwritten signature from the user;

altering an appearance of at least the digital image based, at least in part, on the electronic handwritten signature;

associating the electronic document with the altered signature document as a signed electronic document; and

transmitting the signed electronic document for verification, wherein the signed electronic document is verified by at least comparing the embedded one-way hash to a one-way hash computed from the electronic document during verification.

2. The method of claim 1, further comprising:

providing the signed electronic document to the source device.

3. The method of claim 1, wherein the electronic document is generated by the source device.

4. The method of claim 1, wherein preventing alterations to the electronic document comprises using a limited functionality signing device and one or more security features of the device.

5. The method of claim 1, wherein the embedded one-way hash comprises a checksum.

6. The method of claim 1, further comprising encrypting the embedded one-way hash, and wherein embedding a digital watermark representing the embedded one-way hash in an arbitrary digital representation comprises embedding a digital watermark representing the encrypted one-way hash.

7. The method of claim 6, wherein encrypting the one-way hash comprises using a private key associated with the signing device.

8. The method of claim 1, wherein the digital image comprises a graphical representation of the signature document and altering the appearance of at least the digital image comprises:

applying a visual representation of the electronic handwritten signature to the graphical representation of the signature document.

9. The method of claim 8, wherein the visual representation of the handwritten signature comprises a black line.

10. A signing device comprising:

an external interface configured to receive an electronic document from a source device;

a user interface configured to present the received electronic document to a user and receive a user input;

a processor configured to;

identify a signature document including a digital image embedded with a digital watermark, wherein the digital watermark is an image that represents a watermark and overlays at a least a portion of the digital image and embeds in the signature document, independent of any private key of a user, a one-way hash calculated using the electronic document;

in connection with presenting the signature document including the watermark image applied to the digital image, receive an electronic handwritten signature from the user;

alter an appearance of at least the digital image based, at least in part, on the electronic handwritten signature;

associate the electronic document with the altered signature document as a signed electronic document;

transmit the signed electronic document for verification, wherein the signed electronic document is verified by at least comparing the embedded one-way hash to a one-way hash computed from the electronic document during verification; and

a security feature to prevent alteration of the received electronic document presented to the user for acceptance.

11. The signing device of claim 10, further comprising:

a memory for storing a private key; and

wherein the processor is further configured to;

encrypt the one-way hash using the private key.

12. The signing device of claim 10, wherein the embedded one-way hash is a checksum.

13. The signing device of claim 10, wherein:

the digital image comprises a graphical representation of the signature document,

the processor is configured to alter the appearance of the graphical representation of the signature document by applying a visual representation of the electronic handwritten signature.

14. The signing device of claim 13, wherein the user interface comprises a touch screen.

15. The signing device of claim 13, wherein the visual representation comprises a black line.

16. The signing device of claim 13, wherein the user further provides a password.

17. A signing device comprising:

an external interface configured to receive an electronic document from a source device;

a user interface configured to present a received electronic document to a user and receive an electronic handwritten signature;

a processor configured to;

generate a signature document including a digital image by calculating a one-way hash for the received electronic document, encrypting the one-way hash independent of any private key of a user and embedding a digital watermark, wherein the digital watermark is an image that represents a watermark and overlays at least a portion of the digital image and embeds the encrypted one-way hash in the signature document;

in connection with presenting the signature document including the watermark image applied to the digital image, receive an electronic handwritten signature from the user;

after embedding the digital watermark in the digital image, alter an appearance of at least the digital image based, at least in part, on the electronic handwritten signature by applying a visual representation of the handwritten signature to the digital image, wherein the digital image comprises a graphical representation of the signature document;

associate the electronic document with the altered signature document as a signed electronic document; and

transmit the signed electronic document for verification, wherein the signed electronic document is verified by at least comparing the embedded one-way hash to a one-way hash computed from the electronic document during verification; and

a security feature to prevent alteration of the received electronic document presented to the user for acceptance.

18. A method comprising:

receiving at a signing device an electronic document provided by a source device;

preventing alterations to the received electronic document present to a user using the signing device;

generating a signature document by calculating a one-way hash for the electronic document and embedding a digital watermark representing the one-way hash, wherein the digital watermark comprises an audio file and embeds the one-way hash in the signature document, independent of any private key of a user;

in connection with presenting the electronic document to the user, receiving a voice recording from the user indicating an acceptance of the received electronic document;

altering the signature document by overlaying the voice recording over the audio file;

associating the electronic document with the altered signature document as a signed electronic document; and

transmitting the signed electronic document for verification, wherein the signed electronic document is verified by at least comparing the embedded one-way hash to a one-way hash computed from the electronic document during verification.

19. A signing device comprising:

an external interface configured to receive an electronic document from a source device;

a user interface configured to receive a user input;

a processor configured to;

generate a signature document by calculating a one-way hash for the electronic document and embedding a digital watermark representing the one-way hash, wherein the digital watermark comprises an audio file and embeds the one-way hash in the signature document, independent of a private key of a user;

in connection with presenting the received electronic document to the user, receive a voice recording from a user indicating an acceptance of the received electronic document;

alter the signature document by overlaying the voice recording over the audio file;

associate the electronic document with the altered signature document as a signed electronic document; and

transmit the signed electronic document for verification, wherein the signed electronic document is verified by at least comparing the embedded one-way hash to a one-way hash computed from the electronic document during verification; and

a security feature to prevent alteration of the received electronic document.