Method and system for providing secure key distribution in a communication system

Claim 3

The method according to claim 1, further comprising the steps of: computing (508,517) the value of a third function by each user of said sub-group, said user's third function depending upon at least said user's key (K as ), said user's nonce (N as ) and said group key (K ab ); transmitting (509,518) the value of said user's third function from each user of said sub-group to said server through an available path of said system; and re-computing (510,519) the value of said user's third function for each user of said sub-group by said server and authenticating each user of said sub-group if said re-computed value if equal to the value of said user's third function received by said user.

Claim 7

The method according to claim 5, wherein said group key (K ab ) is extracted by each user of said sub-group by re-computing the value of said user's encryption function and XOR-ing said result with the value of said user's second function.

Claim 10

A communication system (100) for providing secure, authenticated distribution of a key to be used by a group of selected users (101,102,103,109), the key being distributed from a server (109) to a sub-group of users (101,102,103) consisting of the users of said group other than said server, each user of said sub-group sharing a corresponding secret user key with said server, said system comprising: means for transmitting (501,511) the user's identification, a user's nonce and an identification of a user of said sub-group other than said user from each user of said sub-group to said server through an available path of said system; means for generating (502) a new, common group key for all users of said group by said server; means for computing (503,512) the value of a first function for each user of said sub-group by said server, said first function depending upon at least said user's key, said user's nonce, said group key and the identification of the user of said group other than said user; means for computing (504,513) the value of a second function for each user of said sub-group by said server, said second function depending upon at least said user's key, the value of said user's first function and said group key; means for transmitting (505,514) the values of said user's first and second functions from said server to each user of said sub-group through an available path of said system; means for extracting (506,515) said group key, by each user of said sub-group, from the value of said user's second function, employing said user's key and the value of said user's first function; and means for re-computing (507,516) the value of said user's first function by each user of said sub-group and considering authenticated said extracted group key if said re-computed value is equal to the value of said user's first function received by said server.

Claim 11

A communication system (100) for providing secure, authenticated distribution of a key to be used by a group of selected users (101,102,103,109), the key being distributed from a server (109) to a sub-group of users (101,102,103) consisting of the users of said group other than said server, each user of said sub-group sharing a corresponding secret user key with said server, said system comprising: means for transmitting (501,511) the user's identification, a user's nonce and an identification of a user of said sub-group other than said user from each user of said sub-group to said server through an available path of said system; means for generating (502) a new, common group key for all users of said group by said server; means for computing (503,512) the value of a first function for each user of said sub-group by said server, said first function depending upon at least said user's key, said user's nonce, said group key and the identification of the user of said group other than said user; means for computing (504,513) the value of a second function for each user of said sub-group by said server, said second function depending upon at least said user's key, the value of said user's first function and said group key; means for transmitting (505,514) the values of said user's first and second functions from said server to each user of said sub-group through an available path of said system; means for extracting (506,515) said group key, by each user of said sub-group, from the value of said user's second function, employing said user's key and the value of said user's first function; and means for re-computing (507,516) the value of said user's first function by each user of said sub-group and considering authenticated said extracted group key if said re-computed value is equal to the value of said user's first function received by said server.

Claim 12

The communication system according to claim 9, further comprising: means for computing (508,517) the value of a third function by each user of said sub-group, said user's third function depending upon at least said user's key, said user's nonce and said group key; means for transmitting (509,518) the value of said user's third function from each user of said sub-group to said server through an available path of said system; and means for re-computing (510,519) the value of said user's third function for each user of said sub-group by said server and authenticating each user of said sub-group if said re-computed value is equal to the value of said user's third function received by said user.

Claim 13

The method according to claim 3, wherein said first, second and third functions are encryption functions under said user's key (K as ).

Claim 14

The method according to claim 3, wherein said second function is an encryption function under said user's key (K as ) of at least said user's first function, exclusively OR-ed with said group key (K ab ).

Claim 15

The method according to claim 4, wherein said second function is an encryption function under said user's key (K as ) of at least said user's first function, exclusively OR-ed with said group key (K ab ).

Claim 16

The method according to claim 3, further characterized in that: the information to be transmitted from each user of said sub-group to the server is collected by one of the users of the system and then transmitted from said one user to said server.

Claim 17

The method according to claim 4, further characterized in that: the information to be transmitted from each user of said sub-group to the server is collected by one of the users of the system and then transmitted from said one user to said server.

Claim 18

The method according to claim 5, further characterized in that: the information to be transmitted from each user of said sub-group to the server is collected by one of the users of the system and then transmitted from said one user to said server.

Claim 19

The method according to claim 6, further characterized in that: the information to be transmitted from each user of said sub-group to the server is collected by one of the users of the system and then transmitted from said one user to said server.

Claim 20

The method according to claim 3, further characterized in that: the information to be transmitted over the system is identified by a tag identifying the addressed user or server.

Claim 21

The method according to claim 4, further characterized in that: the information to be transmitted over the system is identified by a tag identifying the addressed user or server.

Claim 22

The method according to claim 5, further characterized in that: the information to be transmitted over the system is identified by a tag identifying the addressed user or server.

Claim 23

The method according to claim 6, further characterized in that: the information to be transmitted over the system is identified by a tag identifying the addressed user or server.

Claim 24

The method according to claim 7, further characterized in that: the information to be transmitted over the system is identified by a tag identifying the addressed user or server.