Unpredictable blind signature systems

• US 4,991,210 A
• Filed: 05/04/1989
• Issued: 02/05/1991
• Est. Priority Date: 05/04/1989
• Status: Expired due to Term

• Current Assignee: Van Detsan Networks LLC (Intellectual Ventures LLC)
• Original Assignee: David Chaum
• Inventors: Chaum, David
• Primary Examiner(s): Buczinski, Stephen C.
• Assistant Examiner(s): GREGORY, BERNARR E
• Application Number:
  US07/347,303
• Time in Patent Office: 642 Days
• Field of Search: 380/6, 380/9, 380/28, 380/30, 380/44, 380/49, 380/50, 380/23, 380/25
• US Class Current: 380/30
• CPC Class Codes: G06Q 20/3825 Use of electronic signatures
• CPC Class Codes: G07F 7/1016 Devices or methods for securing the PIN and other transaction-data, e.g. by encryption arrangements for secret communication, see H04L9/00
• CPC Class Codes: H04L 9/302 involving the integer factorization problem, e.g. RSA or quadratic sieve [QS] schemes
• CPC Class Codes: H04L 9/3257 using blind signatures

Abstract

Blind signature systems secure against chosen message attack are disclosed. Multiple candidate original messages can be accommodated. Each of plural candidates in the final signature can be marked by the party issuing the signature in a way that is unmodifiable by the party receiving the signatures. The exponents on the candidates in the final signature need not be predictable by either party. In some embodiments, these exponents are not at all or are only partly determined by the candidates in the signature shown. Single candidate signatures are also accommodated.

Claims

1. In a public-key digital blind signature method, the improvement comprising the steps of:

providing at least one candidate message by a providing party to a blind signature issuing party;

receiving at least one candidate message by said issuing party;

applying, by said issuing party, a public exponent that cannot be determined by said providing party, to at least one of said candidate messages received;

returning, by said issuing party, a resulting first signature including said exponent to said providing party; and

forming by said issuing party of a second digital signature using said at least one candidate message that is unlinkable to said first signature.

2. In a public-key digital blind signature method, the improvement comprising the steps of:

providing at least one candidate message by a providing party to a blind signature issuing party;

receiving at lest one candidate message by said issuing party;

applying, by said issuing party, a public exponent that is independent of the message content of said at least one candidate message and that is different for different signatures issued, to said at least one candidate message received;

returning, by said issuing party, a resulting first signature including said exponent to said providing party; and

forming by said issuing party of a second digital signature using said at least one candidate message that is unlinkable to said first signature.

3. In public-key digital blind signature apparatus, the improvement comprising:

means for providing at least one candidate message by a providing party to a blind signature issuing party;

means for receiving at least one candidate message by said issuing party;

means for applying an exponent by said issuing party, that cannot readily be determined by said providing party, to at least one of said candidate messages received;

means for returning a resulting first signature including said exponent by said issuing party to said providing party; and

means for forming by said issuing party of a second digital signature using said at least one candidate message that is unlinkable to said first signature issued.

4. In public-key digital blind signature apparatus, the improvement comprising:

means for providing at least one candidate message by a providing party to a blind signature issuing party;

means for receiving at least one candidate message by said issuing party;

means for applying an exponent by said issuing party, with the exponent independent of the message content of said at least one candidate message received, and that is different for different messages issued, to at least one of said candidate messages;

means for returning a resulting first signature including said exponent by said issuing party to said providing party; and

means for forming by said issuing party of a second digital signature using said at least one candidate message that is unlinkable to said first signature issued.