Secure cryptographic methods for electronic transfer of information
First Claim
1. A method for a user-controlled first computing device to reduce the computational burden of a tamper-resistant second computing device, the second computing device having a first and second secret key and having to perform a cryptographic action with respect to a public key corresponding to the first secret key, the method comprising the steps of:
- computing by a third computing device, at least one number, by applying a one-way function to the second secret key and a first serial number;
providing by the third computing device to the first computing device, the at least one number;
computing by the first computing device, information based on the at least one number, the information being synchronized with a second serial number of the tamper-resistant computing device;
providing by the first computing device to the second computing device, the information;
computing by the second computing device, at least one output, the output being based on the first secret key, the information, and an application of the one-way function to at least the second secret key and the second serial number; and
updating by the second computing device, the second serial number by applying an update function.
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0 Petitions
Accused Products
Abstract
Cryptographic methods and apparatus are disclosed relating to practical cryptographic systems for electronic transfer of information. Specifically, inventive techniques are described to allow the use of tamper-resistant computing devices without powerful processors; to guarantee security against criminals able to gain full control over computing devices of other parties; to allow value in privacy-protected off-line cash systems to be represented by counters instead of digital coins, without significantly compromising security against criminals who can by-pass tamper-resistance; and to allow secure currency conversion in privacy-protected off-line cash systems, without requiring tamper-resistance for receiver parties.
133 Citations
16 Claims
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1. A method for a user-controlled first computing device to reduce the computational burden of a tamper-resistant second computing device, the second computing device having a first and second secret key and having to perform a cryptographic action with respect to a public key corresponding to the first secret key, the method comprising the steps of:
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computing by a third computing device, at least one number, by applying a one-way function to the second secret key and a first serial number; providing by the third computing device to the first computing device, the at least one number; computing by the first computing device, information based on the at least one number, the information being synchronized with a second serial number of the tamper-resistant computing device; providing by the first computing device to the second computing device, the information; computing by the second computing device, at least one output, the output being based on the first secret key, the information, and an application of the one-way function to at least the second secret key and the second serial number; and updating by the second computing device, the second serial number by applying an update function. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method for implementing a privacy-protected off-line electronic cheque system, in which an account holder holds a tamper-resistant first computing device and a user-controlled second computing device, and electronic cash is issued by an issuing party, the method comprising the steps of:
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computing by the first computing device and the second computing device with the assistance of the issuing party, a first secret key, a corresponding public key and a digital certificate of the issuing party on the public key, the public key and the digital certificate being hidden from the issuing party, the first secret key comprising information certified by the issuing party, and the information certified by the issuing party comprising a second secret key of the first computing device; receiving by the first computing device, a message specifying at least an amount of electronic cash; updating by the first computing device a counter variable in accordance with the amount of electronic cash specified in the message; computing by the first computing device, at least one output based on at least the message and the second secret key; providing by the second computing device to a receiving party, the public key, the digital certificate, and a digital signature on the message with respect to the public key; and verifying by the receiving party, the digital certificate and the digital signature on the message. - View Dependent Claims (12, 13, 14, 15, 16)
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Specification