System and method for using acoustic digital signature generator as oracle

Abstract

A hand-held sonic token can be used as a pseudorandom oracle for a requesting application, which can generate a challenge that is sent to the token. The user of the token decides whether to allow the token to function as an oracle, and if so, the user causes the token to digitally sign the challenge and send it back to the requesting application, for use of the digitally signed challenge as an encryption key. After encryption the requesting application deletes the signed challenge, with subsequent decryption essentially following the encryption process.

What is claimed is:  
     
         1 . A method for encryption, comprising: 
 generating a challenge;    acoustically sending the challenge to a portable token;    deciding whether to allow the token to function as a pseudorandom oracle, and if so, causing the token to digitally sign the challenge to render a signed challenge;    acoustically transmitting the signed challenge; and    using the signed challenge to encrypt data.    
     
     
         2 . The method of  claim 1 , wherein the challenge is generated by a requesting application, the requesting application encrypting data using the signed challenge and deleting the signed challenge after use.  
     
     
         3 . The method of  claim 2 , wherein the challenge is displayed in human readable form to facilitate the deciding act.  
     
     
         4 . The method of  claim 1 , wherein the token digitally signs the challenge at least in part by combining the challenge with a private key.  
     
     
         5 . The method of  claim 4 , wherein the private key is a secret and has a corresponding public key.  
     
     
         6 . The method of  claim 4 , wherein the signed challenge is generated using a process that always renders a first signed challenge when presented with a first challenge.  
     
     
         7 . The method of  claim 6 , wherein the token digitally signs the challenge at least in part by combining the challenge with the private key and with a pseudorandom number (PN), and the method further comprises: 
 storing the PN and reusing the PN upon a second receipt of the challenge to sign the challenge.    
     
     
         8 . A system for encryption, comprising: 
 at least one requesting application transmitting at least one challenge to at least one token using a wireless communication path; and    at least one token receiving the challenge and digitally signing it with at least one private key to render a signed challenge, the token transmitting the signed challenge to the requesting application using a wireless communication path, the requesting application using the signed challenge to encrypt data.    
     
     
         9 . The system of  claim 8 , wherein the requesting application deletes the signed challenge after encrypting data.  
     
     
         10 . The system of  claim 8 , wherein the token displays the challenge to a user to facilitate the user deciding whether to permit the token to sign the challenge and/or to transmit the challenge.  
     
     
         11 . The system of  claim 8 , wherein the wireless communication path is an acoustic path.  
     
     
         12 . The system of  claim 8 , wherein the signed challenge is generated using a process that always renders a first signed challenge when presented with a first challenge.  
     
     
         13 . The system of  claim 12 , wherein the token digitally signs the challenge at least in part by combining the challenge with the private key and with a pseudorandom number (PN), and the token stores the PN after signing the challenge and reuses the PN upon a second receipt of the challenge to sign the challenge.  
     
     
         14 . An encryption system, comprising: 
 acoustic means for transmitting a challenge from a requesting application;    means for receiving the challenge and generating a signed challenge in response;    acoustic means for transmitting the signed challenge to the requesting application; and    means for encrypting data associated with the requesting application using the signed challenge.    
     
     
         15 . The system of  claim 14 , wherein the means for receiving and generating generates the signed challenge only in response to receiving authorization to do so from a user.  
     
     
         16 . The system of  claim 14 , wherein the means for receiving and generating always generates the same signed challenge in response to the challenge.  
     
     
         17 . The system of  claim 14 , wherein the means for receiving and generating includes a hand-held sonic token.  
     
     
         18 . The system of  claim 15 , further comprising means for displaying the challenge.  
     
     
         19 . The system of  claim 14 , wherein the means for receiving and generating digitally signs the challenge at least in part by combining the challenge with a private key and with a pseudorandom number (PN).  
     
     
         20 . The system of  claim 19 , further comprising: 
 means for, when a challenge is signed, storing the PN and reusing the PN upon a second receipt of the challenge to sign the challenge.