Undeniable certificates for digital signature verification

• US 6,292,897 B1
• Filed: 11/03/1997
• Issued: 09/18/2001
• Est. Priority Date: 11/03/1997
• Status: Expired due to Term

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Gennaro, Rosario, Krawczyk, Hugo Mario, Rabin, Tal D.
• Primary Examiner(s): Barron, Jr., Gilberto
• Assistant Examiner(s): DI LORENZO, ANTHONY
• Application Number:
  US08/963,343
• Time in Patent Office: 1,415 Days
• Field of Search: 380/23, 380/21, 380/285, 713/156, 713/155, 713/175, 713/180
• US Class Current: 713/175
• CPC Class Codes: H04L 9/321 involving a third party or a trusted authority
• CPC Class Codes: H04L 9/3247 involving digital signatures
• CPC Class Codes: H04L 9/3263 involving certificates, e.g. public key certificate [PKC] or attribute certificate [AC]; Public key infrastructure [PKI] arrangements network architectures or network communication protocols for supporting authentication of entities using certificates in a packet data network H04L63/0823

Abstract

A signer uses an undeniable signature scheme to sign his public key to thereby create an “undeniable certificate” which can be used to verify the signer'"'"'s digital signature on any message signed using the signer'"'"'s corresponding private key. Hence, once the undeniable certificate is received by the recipient, the recipient and the signer engage one time in a confirmation protocol or denial protocol to the satisfaction of the recipient that the undeniable certificate has in fact been signed by the signer thus certifying signer'"'"'s public key. Thereafter, the recipient can use the certified public key to verify any documents signed by the signer with no further interaction with the signer. However, third parties are precluded from verifying the signer'"'"'s signature since they do not possess the confirmed undeniable certificate and corresponding public key. Digital signatures can now be verified between two parties using a public key as in traditional digital signatures but which avoids verifiability by third parties.

Claims

1. A method for generating an undeniable certificate from a signer to a recipient wherein said signer sends said undeniable certificate thereby eliminating the need for a trusted third partly, said method comprising the steps of:

generating a first key pair for an undeniable signature scheme comprising a first private signing key and a corresponding first public verification key, said first public vertification key for verifying undeniable signatures generated under the first private signing key,

generating a second key pair for a digital signature scheme comprising a second private signing key and a corresponding second public verification key, said second public verification key for verifying a signature on a message generated with the second private signing key;

signing said second public verification key by the signer using the first undeniable private signing key to generate an undeniable certificate of the second public verification key;

sending to the recipient said undeniable certificate of the second public verification key; and

interacting in a confirmation protocol between said signer and said recipient, said signer needing no prior knowledge of said recipient, using the first undeniable public verification key to verify to the recipient that said undeniable certificate was signed using the first undeniable provide signing key, said recipient accepting or rejecting said undeniable certificate.

2. A method for generating an undeniable certificate from a signer to a recipient as recited in claim 1 wherein the interacting step comprises a single message from the signer to the recipient.

3. A method for generating an undeniable certificate from a signer to a recipient as recited in claim 1 wherein said undeniable signature scheme comprises a chameleon signature scheme.

4. A method for generating an undeniable certificate from a signer to a recipient as recited in claim 1 wherein said digital signature scheme is a chameleon signature scheme.

5. A method for generating an undeniable certificate from a signer to a recipient as recited in claim 2 wherein said digital signature scheme is a chameleon signature scheme.

6. A method for generating an undeniable signature from a signer to a recipient on a message, wherein said signer sends said undeniable certificate thereby eliminating the need for a trusted third party, comprising the steps:

generating a first key pair an undeniable signature scheme comprising a first private signing key and a corresponding first public vertification key, said first private signing key for verifying undeniable signatures generated under the first private signing key;

generating a second key pair for a digital signature scheme comprising a second private signing key and a corresponding public verification key, said second public verification key for verifying a signature on a message generated with the second private signing key;

signing said second public vertification key by the signer using the first undeniable private signing key to generate an undeniable certificate of the second public verification key;

sending to the recipient said undeniable certificate of the second public verification key;

interacting in a confirmation protocol between said signer and said recipient, said signer needing no prior knowledge of said recipient, using the first undeniable public verification key to verify to the recipient that said undeniable certificate was signed using the first undeniable private signing key, said recipient accepting or rejecting said undeniable certificate;

the signer signing a message to create a signature using the second signing key associated with the second verification key certified by said undeniable certificate; and

the recipient verifying said signature with the second vertification key certified by said undeniable certificate.

7. A method for generating an undeniable signature from a signer to a recipient on a message as recited in claim 6 wherein the interacting step comprises a single message from the signer to the recipient.

8. A method for generating an undeniable signature from a signer to a recipient on a message as recited in claim 6 wherein said undeniable signature scheme comprises a chameleon signature scheme.

9. A method for generating an undeniable signature from a signer to a recipient on a message as recited in claim 6 wherein said digital signature scheme is a chameleon signature scheme.

10. A method for generating an undeniable signature from a signer to a recipient on a message as recited in claim 7 wherein said digital signature scheme is a chameleon signature scheme.

11. A computer readable medium containing code for operating a computer system to generate an undeniable certificates from a signer to a recipient thereby eliminating the need for a trusted third party, wherein said signer sends said undeniable certificate, said code implementing the steps of:

generating a first key pair for an undeniable signature scheme comprising a first private signing key and a corresponding first public verification key, said first public verification key for verifying undeniable signatures generated under the first private signing key;

generating a second key pair for a digital signature scheme comprising a second private signing key and a corresponding public verification key, said second public vertification key for verifying a signature on a message generated with the second private signing key;

allowing a signer to sign said second public verification key by the signer using the first undeniable private key to generate an undeniable certificate of the second public verification key;

sending to the recipient said undeniable certificate of the second public verification key; and

implementing a confirmation protocol between said signer and said recipient, said signer needing no prior knowledge of said recipient, using the first undeniable public verification key to verify to the recipient that said undeniable certificate was signal using the first undeniable private signing key, said recipient accepting or rejecting said undeniable certificate.

12. A computer readable medium containing code for operating a computer system to generate an undeniable certificate from a signer to a recipient as recited in claim 11 wherein said confirmation protocol comprises a single message from the signer to the recipient.

13. A computer readable medium containing code for operating a computer system to generate an undeniable certificate from a signer to a recipient as recited in claim 11 wherein said undeniable signature scheme comprises a chameleon signature scheme.