Methods and systems for providing a secure data distribution via public networks

Abstract

A server in a public key system stores a list of fingerprints of digital data. Another fingerprint is computed for this list of fingerprints and provided to a client terminal. A client terminal in a public key system obtains a list of fingerprints of digital data from a first source in this system. The client terminal further obtains a fingerprint for that list of fingerprints from a first source as well as from a second source for comparing both obtained fingerprints.

1 .- 139 . (canceled)  
     
     
         140 . A method performed by a server of a public key system, said public key system further comprising a plurality of client terminals, said method comprising the steps of: 
 storing a first list of fingerprints of digitally encoded data;    computing a first fingerprint for at least a part of said list of fingerprints; and    providing said computed first fingerprint.    
     
     
         141 . The method according to  claim 140 , wherein said step of computing said first fingerprint comprises the steps of: 
 obtaining one or more entries of said first list of fingerprints, whereby said one or more entries are to be covered by said first fingerprint; and    computing a hash value on at least said obtained one or more entries.    
     
     
         142 . The method according to  claim 140 , wherein said first list of fingerprints further comprises at least one of the following: 
 a unique identifier associated with each fingerprint;    a time specification associated with each fingerprint, whereby said time specification specifies at least one of a time of entry into said first list associated with said fingerprint or said digital data, a time of generation of said fingerprint or said digital data, or a time of provision of said fingerprint or said digital data to said server; or    a link to digital data or an association with digital data of each fingerprint.    
     
     
         143 . The method according to  claim 141 , wherein said one or more entries in said step of obtaining said computed first fingerprint further comprising at least one of a unique identifier or a time specification associated with a fingerprint.  
     
     
         144 . The method according to  claim 142 , wherein said unique identifier, said time specification, said link or said association are established and assigned by said server as part of said storing step.  
     
     
         145 . The method according to  claim 140 , wherein said step of providing said computed first fingerprint comprises attaching said first fingerprint to a message that is sent to at least one of said plurality of user terminals.  
     
     
         146 . The method according to  claim 140 , wherein said step of providing said computed first fingerprint or said step of computing said first fingerprint further comprises signing said first fingerprint by said server.  
     
     
         147 . The method according to  claim 140 , wherein said step of storing a first list of fingerprints comprises the steps of: 
 receiving digital data;    establishing at least one of the integrity of said digital data, the identity of a sender of said digital data and the authenticity of said sender; whereby said establishing comprises at least one of verifying a digital signature for said digital data, verifying a fingerprint associated with said digital data or sender, using a secure and trusted connection for the communication with said sender, and applying an encryption scheme for the said received digital data;    computing a hash value on at least said digital data; and    adding said hash value to said first list of fingerprints.    
     
     
         148 . The method according to  claim 140 , wherein at least said steps of computing a first fingerprint and providing said computed first fingerprint are performed repeatedly according to a timed schedule, and wherein said first list of fingerprints can be augmented or continued with further entries.  
     
     
         149 . The method according to  claim 148 , wherein said step of providing said computed first fingerprint comprises providing or updating said first fingerprint on an hourly, daily, weekly, monthly or another regular time period basis.  
     
     
         150 . The method according to  claim 140 , wherein said step of providing said computed first fingerprint further comprises associating and providing at least one of a time specification, a validity period information or another identifier providing for establishing the validity of said provisioned first fingerprint.  
     
     
         151 . A method performed by a client terminal of a public key system, said public key system comprising a plurality of client terminals and at least one server, said method comprising the steps of: 
 obtaining a first list of fingerprints of digitally encoded data from a first source;    obtaining a first fingerprint of said list of fingerprints from a first source;    obtaining a second fingerprint of said list of fingerprints from a second source; and    comparing said first and said second fingerprint.    
     
     
         152 . The method according to  claim 151 , further comprising the steps of: 
 computing a fingerprint of said obtained first list of fingerprints;    comparing said computed fingerprint and said obtained first and second fingerprints;    if at least one of said comparing steps result in different fingerprints, establishing that the data integrity of said received fingerprints or said first list of fingerprints has been compromised;    
     
     
         153 . The method according to  claim 151 , further comprising the steps of: 
 obtaining at least one of said digitally encoded data of said fingerprint list;    computing a fingerprint of said obtained digital data;    comparing said computed fingerprint with the fingerprint for said obtained digital data in said received list of fingerprints; and    if said comparing step results in different fingerprints, establishing that the data integrity of said received digital data or said list of fingerprints has been compromised;    
     
     
         154 . The method according to  claim 151 , further comprising at least one of: 
 verifying a digital signature for said received first and second fingerprint;    verifying a digital signature for a received list of fingerprints;    verifying a fingerprint associated with said received first and second fingerprint or said first and second source; and    receiving a user input to perform at least one of said steps of verifying a digital signature and verifying a fingerprint.    
     
     
         155 . The method according to  claim 151 , wherein said steps of obtaining said first and second fingerprint comprising a step of 
 receiving said first and second fingerprint together with a message sent to said client terminal via communications media of a public network connecting said client terminals and said server; and    said method further comprising a step of: 
 attaching a fingerprint of said list of fingerprints to a message sent to another client terminal via said communications media of a public network connecting said client terminals.  
   
     
     
         156 . The method according to  claim 155 , wherein said steps of obtaining said first and second fingerprint and attaching a fingerprint are accomplished automatically without an explicit request by the receiving client terminal of said message but as part of a regular communication between client terminals not established for the purpose of exchanging said first or second fingerprint.  
     
     
         157 . The method according to  claim 151 , wherein said step of attaching a fingerprint further comprises associating and attaching at least one of a time specification, a validity period information or another identifier providing for establishing the validity of said provisioned fingerprint.  
     
     
         158 . The method according to  claim 155 , wherein said step of attaching a fingerprint to a message is only performed for fingerprints that are verified by said client terminal to be valid and authentic; whereby said verification may depend on the number of successful comparing steps that were performed for said attached fingerprint with received corresponding fingerprints of mutually different and/or independent sources; and wherein said step of attaching a fingerprint further comprises signing said fingerprint by said client terminal using a private key of said client terminal.  
     
     
         159 . The method according to  claim 151 , wherein said steps of obtaining said first and second fingerprint comprising a step of 
 determining whether a received fingerprint and/or a received list of fingerprints is valid and represents the latest published version by means of associated or attached information to said received fingerprint and/or received list of fingerprints or by means of a predetermined timed schedule known to said client terminal; and    if said received fingerprint and/or a received list of fingerprints is not valid, disregarding said received fingerprint and/or received list of fingerprints or requesting a fingerprint and/or a list of fingerprints from another source to replace the invalid versions.    
     
     
         160 .- 273 . (canceled)