PREVENTION OF UNAUTHORIZED FORWARDING AND AUTHENTICATION OF SIGNATURES

• US 20080229111A1
• Filed: 03/16/2007
• Published: 09/18/2008
• Est. Priority Date: 03/16/2007
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Benaloh, Josh, Paya, Cem
• Granted Patent: US 8,090,954 B2
• Time in Patent Office: Days
• US Class Current: 713/176
• CPC Class Codes: H04L 2209/56 Financial cryptography, e.g. electronic payment or e-cash
• CPC Class Codes: H04L 2209/80 Wireless network architectures or network communication protocols for wireless network security H04W12/00
• CPC Class Codes: H04L 9/3247 involving digital signatures

Abstract

A forwarding signature comprises a modified digital signature, modified using a predetermined parameter between a sender and an intended recipient. An intended recipient of the forwarding signature can verify that the forwarding signature corresponds to the message, but, can neither derive the original digital signature nor generate a new forwarding signature for a different parameter. Generation and verification of the forwarding signature is accomplished with access to the public key of a public/private cryptographic key pair, the original signed message, and the predetermined parameter. Access to the private key is not needed.

Claims

1. An authentication method comprising:

receiving a message and a modified signature, wherein;

the modified signature is indicative of a signed message, the signed message being signed utilizing a predetermined parameter; and

the signed message is indicative of the message, the message being signed utilizing a private key of a public/private key pair;

operating on the modified signature to generate a first value, wherein the modified signature is operated on utilizing a public key of the public/private key pair;

operating on the message to generate a second value, wherein the message is operated on utilizing the predetermined parameter;

comparing the first value and the second value; and

authenticating the message in accordance with a result of comparing the first value and the second value.

2. A method in accordance with claim 1 wherein the message comprises a cryptographic hash value indicative of the message.

3. A method in accordance with claim 1, wherein the predetermined parameter comprises a cryptographic hash value indicative of a shared parameter.

4. A method in accordance claim 1, wherein:

the public key comprises an exponent value, and

operating on the modified signature comprises raising the signature to a power equal to the exponent value.

5. A method in accordance claim 1, wherein:

operating on the message comprises raising the message to a power equal to the predetermined parameter modulo an integer value.

6. A method in accordance claim 1, wherein:

the message is signed in accordance with a formula;

S=m ^d mod N, wherein;

S represents the signed message;

m represents the message;

d represent a exponent value of the private key; and

N represents an integer value; and

the modified signature is modified in accordance with a formula;

T=S ^p mod N, wherein;

T represents the signature; and

p represents the predetermined parameter.

7. A method in accordance with claim 6, wherein:

the modified signature is operated on in accordance with a formula;

T^e mod N, wherein e represents an exponent parameter of the public key; and

the message is operated on in accordance with a formula;

m^p mod N.

8. A authentication system comprising:

an input/output portion configured to receive a message and a modified signature, wherein;

the modified signature is indicative of a signed message, the signed message being signed utilizing a predetermined parameter; and

the signed message is indicative of the message, the message being signed utilizing a private key of a public/private key pair;

a processing portion configured to;

operate on the modified signature to generate a first value, wherein the modified signature is operated on utilizing a public key of the public/private key pair;

operate on the message to generate a second value, wherein the message is operated on utilizing the predetermined parameter;

compare the first value and the second value; and

authenticate the message in accordance with a result of comparing the first value and the second value.

9. A system in accordance with claim 8 wherein the message comprises a cryptographic hash value indicative of the message.

10. A system in accordance with claim 8, wherein the predetermined parameter comprises a cryptographic hash value indicative of a shared parameter.

11. A system in accordance claim 8, wherein:

the public key comprises an exponent value, and

operating on the modified signature comprises raising the signature to a power equal to the exponent value.

12. A system in accordance claim 8, wherein:

operating on the message comprises raising the message to a power equal to the predetermined parameter modulo an integer value.

13. A system in accordance claim 8, wherein:

the message is signed in accordance with a formula;

S=m ^d mod N, wherein;

S represents the signed message;

m represents the message;

d represent a exponent value of the private key;

mod represents a modular reduction function; and

N represents an integer value; and

the modified signature is modified in accordance with a formula;

T=S ^p mod N, wherein;

T represents the signature; and

p represents the predetermined parameter.

14. A system in accordance with claim 13, wherein:

the modified signature is operated on in accordance with a formula;

T ^e mod N;

wherein e represents an exponent parameter of the public key; and

the message is operated on in accordance with a formula;

m ^p mod N.

15. A computer-readable medium having stored thereon computer-executable instructions for performing authentication by performing the steps of:

receiving a message and a modified signature, wherein;

the modified signature is indicative of a signed message, the signed message being signed utilizing a predetermined parameter; and

the signed message is indicative of the message, the message being signed utilizing a private key of a public/private key pair;

operating on the modified signature to generate a first value, wherein the signature is operated on utilizing a public key of the public/private key pair;

operating on the message to generate a second value, wherein the message is operated on utilizing the predetermined parameter;

comparing the first value and the second value; and

authenticating the message in accordance with a result of comparing the first value and the second value.

16. A computer-readable medium in accordance with claim 15 wherein the message comprises a cryptographic hash value indicative of the message.

17. A computer-readable medium in accordance with claim 15, wherein the predetermined parameter comprises a cryptographic hash value indicative of a shared parameter.

18. A computer-readable medium in accordance claim 15, wherein:

the public key comprises an exponent value, and

operating on the modified signature comprises raising the signature to a power of the exponent value.

19. A computer-readable medium in accordance claim 15, wherein:

operating on the message comprises raising the message to a power equal to the predetermined parameter modulo an integer value.

20. A computer-readable medium in accordance claim 15, wherein:

the message is signed in accordance with a formula;

S=m ^d mod N, wherein;

S represents the signed message;

m represents the message;

d represent a exponent value of the private key;

mod represents a modular reduction function; and

N represents an integer value; and

the modified signature is modified in accordance with a formula;

T=S ^p mod N, wherein;

T represents the signature; and

p represents the predetermined parameter; and

the modified signature is operated on in accordance with a formula;

T ^e mod N;

wherein e represents an exponent parameter of the public key; and

the message is operated on in accordance with a formula;

m ^p mod N.