Electronic signing apparatus and methods

• US 8,583,931 B2
• Filed: 08/09/2007
• Issued: 11/12/2013
• 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:
  US11/836,485
• Publication Number:
  US 20070277042A1
• Time in Patent Office: 2,287 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 system comprising:

a source device including;

an interface configured to;

receive an electronic document;

transmit the electronic document to a dedicated signing device; and

receive a signed electronic document from the dedicated signing device, the signed electronic document including the electronic document and an associated signature document including a digital image embedded with a digital watermark representing an encrypted one-way hash;

memory configured to store a public key assigned to the dedicated signing device;

a processor configured to;

calculate a one-way hash of the electronic document;

decode the digital watermark representing the encrypted one-way hash;

decrypt the encrypted one-way hash using the stored public key assigned to the dedicated signing device;

compare the decrypted one-way hash to the calculated one-way hash; and

wherein the dedicated signing device includes;

a signer interface configured to receive input from a signer;

an external interface configured to;

receive the electronic document from the source device;

transmit the signed electronic document to the source device, the signed electronic document including the electronic document and the associated signature document;

memory configured to store a private key assigned to the dedicated signing device; and

a processor configured to;

prevent alterations to the electronic document presented by the dedicated signing device;

alter a characteristic of the signature document based on the signer input, the signature document comprising an arbitrary digital representation;

calculate the one-way hash for the electronic document;

encrypt the one-way hash using the stored private key assigned to the dedicated signing device;

embed the digital watermark representing the encrypted one-way hash into the arbitrary digital representation, wherein the digital watermark is generated and embedded independent of any private key of the signer; and

associating the electronic document with the altered signature document as the signed electronic document.

2. The system of claim 1, wherein the arbitrary digital representation is a digital image;

the signer input is a handwritten signature; and

altering the characteristic of the arbitrary digital representation comprises applying a visual representation of the handwritten signature to a graphical representation of the signature document.

3. The system of claim 1, wherein the signer interface comprises a touch screen.

4. The system of claim 1, wherein the signer input comprises a password.

5. The system of claim 1, the arbitrary digital representation comprising an audio file, the signer input comprising a voice recording, the processor of the dedicated signing device further configured to alter a characteristic of the signature document based on the signer input by overlaying the voice recording over the audio file.

6. The system of claim 1, wherein the one-way hash is a checksum.

7. The system of claim 1, wherein the arbitrary digital representation is a digital image, the processor of the dedicated signing device further configured to alter the characteristic of the signature document based on the signer input by applying a visual representation of the user input to a graphical representation of the signature document.

8. The system of claim 7, wherein the visual representation of the signer input comprises a black line.

9. The system of claim 1, wherein the signer input comprises biometric data.

10. The system of claim 9, wherein the biometric data is a handwritten signature.

11. A method, comprising:

storing at a signing device a private key assigned to the signing device;

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

preventing alterations to the electronic document presented by the dedicated signing device;

generating a signature document by calculating a first one-way hash for the electronic document, encrypting the first one-way hash using the private key assigned to the dedicated signing device, and embedding a digital watermark representing the encrypted first one-way hash in a first image, wherein the digital watermark is generated and embedded independent of any private key of a signer;

altering a characteristic of the signature document based on a signer input;

associating the electronic document with the signature document, wherein the electronic document and the signature document together comprise a signed electronic document;

storing at a server a plurality of public keys assigned to different signing devices including a public key assigned to the signing device;

receiving, at the server, the signed electronic document comprising the electronic document and the signature document, the signer input including an electronic handwritten signature applied to the first image and the digital watermark;

verifying an integrity of the digital watermark based, at least in part, on an integrity of the electronic handwritten signature applied to the image;

decrypting, using the public key assigned to the dedicated signing device, the first one-way hash embedded in the first image in connection with at least determining the integrity of the digital watermark;

calculating a second one-way hash for the electronic document;

comparing the first one-way hash to the second one-way hash; and

verifying contents of the signed electronic document based at least in part on the one-way hash comparison.

12. The method of claim 11, further comprising providing the signed electronic document to the source device.

13. The method of claim 11, wherein the electronic document is generated by the source device.

14. The method of claim 11, wherein an arbitrary digital representation comprises a digital image, the signer input comprises biometric data and altering the characteristic of the signature document comprises:

applying a visual representation of the biometric data to a graphical representation of the signature document.

15. The method of claim 14, wherein the biometric data comprises a handwritten signature.

16. The method of claim 15, wherein the visual representation of the handwritten signature comprises a black line.