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US 6,148,084 AGranted
Restrictedly blindable certificates on secret keys
AssigneeNone recorded
InventorStefanus A. Brands
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AssigneeNone recorded
InventorStefanus A. Brands
Estimating the term…
A method for an issuer party to issue DSA-like secret-key certificates that can be blinded only restrictively. The method includes the step of generating a secret key (x.sub.0,y) and a public key (descr(G.sub.q), g, h.sub.0, g.sub.1, descr((.cndot.))), wherein q is a prime number, Gq is a group of order q, in which computing discrete logarithms is substantially infeasible, but in which multiplication, determination of equivalence of elements and generation of substantially random numbers is relatively easy, descr(G.sub.q) is a description of G.sub.q including q, descr((.cndot.)) is the description of a hash-function (.cndot.) for which computing inverses is substantially infeasible, x.sub.0, and y are elements of the ring, of integers modulo q, g is an element of order q in the group, G.sub.q, h.sub.o is equal to g.sup.x.sbsp.0 ; and g.sub.1 is equal to g.sup.y. The method further includes the step of issuing to a receiver party a secret-key certificate (r,a) in on a public key h in G.sub.q, the secret key certificate being generated with a computer such that (g.sup.d/c h.sup.r/c) mod q is equal to a, where c is computed by applying (.cndot.) to at least h.
A method for an issuer party to issue secret-key certificates that can be blinded only restrictively, the method comprising the steps of:
Dependencies are inferred from the claim text.
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No related US applications are recorded in the indexed filing history.
Payment circuits: private payment circuits, e.g. involving electronic currency used among participants of a common payment scheme
Payment architectures, schemes or protocols: involving a neutral party, e.g. certification authority, notary or trusted third party [TTP]
Involving electronic purses or money safes: e-cash details, e.g. blinded, divisible or detecting double spending
Insuring higher security of transaction: combining multiple encryption tools for a transaction
Term ended 5 Dec 2017 (estimated)
USPTO file history isn’t available for this patent, so only indexed dates are shown.
1. Field of the Invention
The present invention relates to cryptographic techniques, and more particularly to systems for issuing and showing of DSA-like secret-key certificates that can be blinded only restrictively.
2. Description of the Prior Art
Other features, objects, and advantages of this invention will be appreciated when the description and appended claims are read in conjunction with the figures.
FIG. 1 shows a flowchart of a restrictive blind issuing protocol for DSA-like secret-key certificates, in accordance with the teachings of the present invention.
FIG. 2 shows a flowchart of a first coin withdrawal protocol based on the restrictive blind secret-key certificate issuing protocol of FIG. 1, in accordance with the teachings of the present invention.
In accordance with these and other objects of this invention, a brief summary of the invention is presented. Some simplifications and omissions may be made in the following summary, which is intended to highlight and introduce some aspects of the present invention, but not to limit its scope. Detailed descriptions of preferred exemplary embodiments adequate to allow those of ordinary skill in the art to make and use this invention will be provided later.
In an issuing protocol for secret-key certificates, a designated party called a Certification Authority issues triples. Each triple consists of a secret key, a corresponding public key and a certificate of the Certification Authority on the public key. If the issuing protocol is restrictive blind, then a receiver party that obtains such a triple can ensure that the public key and the certificate are uncorrelated to the view of the Certification Authority; but on the other hand the receiver party cannot dispose information into this predicate of the secret key, and so the Certificate Authority can encode information into this predicate of the secret key. This property should preferably hold even when executions of the issuing protocol can be performed in parallel without limitation. A summary of the forming of secret-key certificates in accordance with the present invention follows.
The secret key of the Certification Authority is a pair (x.sub.0,y) in where q is a prime number. The symbol denotes the set of numbers {0, . . . , q-1}, with addition and multiplication defined modulo q. The corresponding public key of the Certification Authority is (descr(G.sub.q),g,h.sub.0,g.sub.1, descr((.cndot.))), whereby G.sub.q is a multiplicative group containing q elements and descr(G.sub.q) denotes a description of G.sub.q including q; g is an element of order q in the group G.sub.q ; h.sub.0 is equal to g.sup.x.sbsp.0 ; g.sub.1 is equal to g.sup.y ; and descr((.cndot.)) is the description of a one-way hash-function, preferably such that it is substantially infeasible to find collisions.