Method and apparatus for roaming use of cryptographic values

• US 20020013898A1
• Filed: 03/26/2001
• Published: 01/31/2002
• Est. Priority Date: 06/04/1997
• Status: Abandoned Application

• Current Assignee: Frank W. Sudia, Peter C. Freund, Stuart T F Huang
• Original Assignee: Frank W. Sudia, Peter C. Freund, Stuart T F Huang
• Inventors: Sudia, Frank W., Freund, Peter C., Huang, Stuart T.F.
• Application Number:
  US09/816,684
• Publication Number:
  US 20020013898A1
• Time in Patent Office: Days
• US Class Current: 713/155
• CPC Class Codes: G06F 7/725 over elliptic curves
• CPC Class Codes: G06Q 20/02 involving a neutral party, e.g. certification authority, notary or trusted third party [TTP]
• CPC Class Codes: G06Q 20/3829 involving key management
• CPC Class Codes: H04L 9/085 Secret sharing or secret splitting, e.g. threshold schemes
• CPC Class Codes: H04L 9/3255 using group based signatures, e.g. ring or threshold signatures

Abstract

A multi-step signing system and method uses multiple signing devices to affix a single signature which can be verified using a single public verification key. Each signing device posesses a share of the signature key and affixes a partial signature in response to authorization from a plurality of authorizing agents. In a serial embodiment, after a first partial signature has been affixed, a second signing device exponentiates the first partial signature. In a parallel embodiment, each signing device affixes a partial signature, and the plurality of partial signatures are multiplied together to form the final signature. Security of the system is enhanced by distributing capability to affix signatures among a plurality of signing devices and by distributing authority us affix a partial signature among a plurality of authorizing agents.

Claims

1. A digital signing method comprising steps of:

generating shares of a private signature key;

storing shares in separate electronic signing devices;

certifying multiple authorizing agents for signing devices; and

for each of a plurality of signing devices, affixing a partial signature to an electronic message in response to authorization from a minimum number of authorizing agents;

wherein a plurality of partial signatures constitutes a digital signature.

2. A system for affixing digital signatures to electronic documents comprising:

a plurality of intercommunicative signing devices, each signing device comprising an electronic device programmed to receive an electronic document and to affix a partial signature using a signature key share in response to a predetermined number of authorizations; and

a plurality of authorizing agents, each agent communicative with an associated signing device, each anent comprising an electronic device programmned to provide an authorization to an associated signing device.

3. A system of interlocked rings of signing devices for affixing digital signatures to electronic documents comprising:

a first set of signing devices, said first set comprising a plurality of electronic devices, each device programmed-to receive an electronic document and affix a partial signature for a first signature key, a plurality of said partial signatures comprising a first digital signature;

a second set of signing devices, said second set comprising a plurality of electronic devices, each device programmed to receive an electronic document and affix a partial signature for a second signature key, a plurality of said partial signatures comprising a second digital signature;

wherein said first includes at least one member which is not in said second set, and said first and second sets include at least one common member.

4. An electronic method for delegated use of an electronic key comprising steps storing said key in a first electronic device;

commnunicating an electronic delegation certificate to a delegate;

sending a request and the delegation certificate from the delegate to the first electronic device; and

using said first electronic device to use the electronic key in response to the request and the delegation certificate.