A little while ago someone posted about a new company that would do patent searches via email requests. For another week they are doing free searches as an introductory offer. I did a search on blind-signature based cash systems, and these are the patents it found. This might be useful for those considering implementing electronic cash. Full text of patents are available for $4.95. The kind of search I did for free will cost $149 after another week. People are allowed 3 searches per day for free until then. For more info send a message with just "help" in the body to spo_patent@spo.eds.com. Hal 2 04977595 19901211 380/24 Method and apparatus for implementing ++electronic++ ++cash++ Inventor: Ohta; Kazuo Assignee: Nippon Telegraph and Telephone Corporation Abstract: In an ++electronic++ ++cash++ implementing method, a user makes a ++bank++ apply a ++blind++ signature to user information Vi produced, by a one-way function, from secret information Si containing identification information, thereby obtaining signed user information. Further, the user makes the ++bank++ apply a ++blind++ signature to information containing authentication information Xi produced, by a one-way function, from random information Ri, thereby obtaining signed authentication information. The user uses an information group containing the signed user information, the signed authentication information, the user information and the authentication information, as ++electronic++ ++cash++ for payment to a ++shop++. The ++shop++ verifies the validity of the signed user information and the signed authentication information, and produces and sends to the user an inquiry. In response to the inquiry the user produces a response Yi by using secret information and random information and sends it to the ++shop++. Having verified the validity of the response the ++shop++ accepts the ++electronic++ ++cash++. 3 05224162 19930629 380/24 ++Electronic++ ++cash++ system Inventor: Okamoto; Tatsuaki Assignee: Nippon Telegraph and Telephone Corporation Abstract: In an ++electronic++ ++cash++ system, K sets of ++blind++ signature information are derived from secret information containing identification information of a user, K/2 sets of them are opened and a ++bank++ attaches a ++blind++ signature to the remaining K/2 sets of information. The user obtains a signed license from the ++blind++ signature. The user generates ++blind++ signature information from the license and a desired amount of money and gets a ++blind++ signature of the ++bank++ to the ++blind++ signature information and obtains ++electronic++ ++cash++ signed by the ++bank++ from the ++blind++ signature. The user presents to a ++shop++ a residue power root of a node in a money hierarchial structure and the ++electronic++ ++cash++, corresponding to the amount of money to be used, and the ++shop++ verifies their validity and, if they are valid, offers inquiry information to the user. The user offers, as response information, a residue power root of the node corresponding to the amount of money to be used to the ++shop++. The ++shop++ verifies the validity of the response information and, if it is valid, acknowledges the payment with ++electronic++ ++cash++ of the amount of money to be used. 4 04759063 19880719 380/30 ++Blind++ signature systems Inventor: Chaum; David L. Abstract: A cryptographic system allows, in one exemplary use, a supplier to cryptographically transform a plurality of messages responsive to secret keys; the transformed messages to be digitally signed by a signer; and the signed transformed messages returned to the supplier to be transformed by the supplier, responsive to the same secret keys, in such a way that a ++digital++ signature related to each original message is developed by the supplier. One important property of these systems is that the signer cannot determine which transformed message received for signing corresponds with which ++digital++ signature-even though the signer knows that such a correspondence must exist. 6 04914698 19900403 380/30 One-show ++blind++ signature systems Inventor: Chaum; David Abstract: Numbers standing for ++cash++ money can be ++spent++ only one time each, otherwise the --account-- from which they were ++withdrawn++ would be revealed. More generally, a technique for issuing and showing ++blind++ ++digital++ signatures ensures that if they are shown responsive to different challanges, then certain information their signer ensures they contain will be revealed and can be recovered efficiently. Some embodiments allow the signatures to be unconditionally untraceable if shown no more than once. Extensions allow values to be encoded in the signatures when they are shown, and for change on unshown value to be obtained in a form that is aggregated and untraceable. 11 04949380 19900814 380/30 Returned-value ++blind++ signature systems Inventor: Chaum; David Abstract: A payer party obtains from a signer party by a ++blind++ signature system a first public key ++digital++ signature having a first value in a withdrawal transaction; the payer reduces the value of the first signature obtained from the first value to a second value and provides this reduced-value form of the signature to the signer in a payment transaction; the signer returns a second ++digital++ signature to the payer by a ++blind++ signature system in online consummation of the payment transaction; the --paper-- derives from the first and the second signature a third signature having a value increased corresponding to the magnitude of the difference between the first and the second values. Furthermore, the following additional features are provided: payments are unlinkable to withdrawals; a ++shop++ between the payer and signer can be kept from obtaining more value than desired by the payer; the first value need not be revealed to the signer or intermediary in the payment transaction; the returned difference can be accumulated across multiple payment transactions; and the returned difference can be divided between a plurality of payment transactions. 19 04759064 19880719 380/30 ++Blind++ unanticipated signature systems Inventor: Chaum; David L. Abstract: An improved ++blind++ signature system not requiring computation during ++blinding++ for anticipating which of a plurality of possible signatures will be made during signing, while still allowing the ++blinding++ party to unblind and recover the unanticipated kind of signature on what was ++blinded++. An exemplary embodiment ++blinds++ by forming a product including a plurality of generators raised to powers normally secret from the signing party, and unblinds by forming a product with the multiplicative inverse of a signed form of the generators raised to the original powers. Re-blinding allows a signature on a value to be transformed into a signature on a particular ++blinded++ form of the value. 23 04206315 19800603 380/23 ++Digital++ signature system and apparatus Inventor: Matyas; Stephen M. Assignee: International Business Machines Corporation Abstract: A ++digital++ signature machine provides a simplified method of forming and verifying a signature that is appended to a ++digital++ message. A sender transmits a signature with the usual signature keys and with validation table entries that correspond to the unsent keys and with the compressed encoding of the next validation table. The receiver uses the compressed encoding of the next validation table to form validation table entries from the signature keys so that the receiver has a full validation table. This validation table is compressed and compared with the compressed encoding which was received from the sender in a preceding message.