Securely using a display to exchange information

Abstract

A first device has a display that is able to show information. The information is to be exchanged with a second device. The information is cleared from the display following receipt of an indication from the second device that the information has been successfully inputted at the second device.

1 . A method for generating a symmetric key, the method comprising:
 generating a first random number at a first device;   generating a first public key based on the first random number;   generating a second random number at the second device; and   generating a second public key based on the second random number.   
     
     
         2 . The method of  claim 1  wherein the first device sends the first public key to the second device. 
     
     
         3 . The method of  claim 1  wherein the second device sends the second public key to the first device. 
     
     
         4 . The method of  claim 1  wherein the first device and second device are one of a mobile device and a smart card reader. 
     
     
         5 . The method of  claim 2  wherein the first device generates a symmetric key based on the first public key and the second public key. 
     
     
         6 . The method of  claim 3  wherein the second device generates a symmetric key based on the first public key and the second public key. 
     
     
         7 . The method of  claim 5  wherein the generation of the symmetric key at the first device occurs before, after or concurrently with the generation of the symmetric key at the second device. 
     
     
         8 . The method of  claim 1  wherein the first and second public keys are calculated based on the formula:
     p=f ( S ) R   A mod  p    
 
     
     
         9 . The method of  claim 5  wherein the symmetric key is calculated based on the formula:
   K=p R   A  mod p