Distributed group key management scheme for secure many-to-many communication

A method of providing secure communications between at least two present members, comprising the steps of:

• providing a binary tree having at least one internal node and at least two leaf nodes, one of said internal nodes being a root node, each of said internal nodes having two branches extending therefrom, a first branch ending at one of said leaf nodes and another branch ending at another of said leaf nodes, a root path extending from each of said leaf nodes to said root node;
• assigning each of said present members to said leaf nodes, whereby each of said present members has a root path extending from a leaf node to said root node;
• assigning a binary ID to said internal nodes and leaf nodes;
• associating a secret key and a blinded key with each of said leaf nodes, wherein the blinded key is derived from the secret key;
• determining a key association group that is associated with a present member for dividing key distribution tasks, the key association group including a group node corresponding to each internal node in the root path of the present member, each group node having an associated member, said present member being assigned to a leaf node in the first branch of said root path internal node, each associated member being assigned to a leaf node in the other branch of said root path internal node;
• the present member sending to the associated member of the key association group a blinded key associated with the group node in the first branch of the root path internal node;
• the key association group associated member sending to the first member a blinded key associated with the group node in the other branch of the root path internal node;
• determining an unblinded key of the root path internal node from the blinded key associated with the other branch group node and the blinded key associated with the first branch group node;
• encrypting data with the root path internal node unblinded key;
• and
• communicating the encrypted data between members located on branches depending from the root path internal node.

A method of joining a new member to a distributed communications system for secure communications between a plurality of local members, comprising the steps of:

• providing a binary tree having at least one internal node and at least two leaf nodes, one of said internal nodes being a root node, each of said internal nodes having two branches extending therefrom, a first branch extending to at least one of said leaf nodes, and a second branch extending to at least another of said leaf nodes, a root path extending from each of said leaf nodes to said root node;
• each of said local members having a binary ID, and being assigned to a leaf node;
• sending a request to join from a new member to one of said local members of the communications system;
• determining a key association group that is associated with the local member for dividing key distribution tasks, the local member key association group including a group node corresponding to each internal node in the root path of the local member, said local member being assigned to a leaf node in the first branch of said root path internal node, said group node having an associated member, each associated member being assigned to a leaf node in the other branch of the root path internal node of the local member;
• granting the request to join;
• splitting the binary ID of the local member into a first ID and a second ID, wherein the first ID is assigned to the local member and the second ID is assigned to the new member;
• generating a local member new secret key;
• generating a new member first secret key;
• generating a local member blinded key from the local member new secret key;
• generating a new member blinded key from the new member first secret key;
• sending the new member blinded key to the local member;
• sending the local member blinded key to the new member;
• calculating the blinded key and the unblinded key of the local member root path internal node;
• sending the local member root path internal node blinded key to the local member key association group associated member corresponding to the group node corresponding to the local member root path internal node;
• sending a blinded key of the group node corresponding to the local member root path internal node to the local member;
• and
• forwarding the group node blinded key corresponding to the local member root path internal node to the new member.

A method of merging a first secure communications system with a second secure communications system, each of said communications systems including a plurality of members having a binary ID, each of said communications systems having a binary tree structure with a root node, said root node having a blinded key, comprising the steps of:

• sending a request to merge the first communications system with the second communications system;
• granting the request to merge;
• using a mixing function to combine the blinded key of the first communications system root node with the blinded key of the second communications system root node;
• appending a 1 to the binary ID of said first communications system plurality of members;
• and
• appending a 0 to the binary ID of each member of the second communications system.

A distributed group key management system for providing secure communication between a plurality of members, comprising:

• at least one sender binary distribution tree for forming a senders group;
• said at least one sender binary distribution tree defining a communication structure having a sender internal node with a first branch and a second branch depending therefrom, each of said branches including a first member assigned to a corresponding leaf node, said first member being associated with a key association group including at least one other member;
• said senders group first member including:
• a unique binary ID associated with the corresponding leaf node to which the senders group first member is assigned;
• a first secret key;
• and
• a blinded key derived from said first secret key for exchanging with a blinded key of the other senders group member;
• wherein said senders group first member uses the blinded key of the at least one other senders group member and the first secret key to calculate an unblinded key of the sender internal node to be used for encrypting and decrypting sending group data that is communicated between sending group members located on branches depending from the sender internal node;
• and
• at least one receiver binary distribution tree for forming a receivers group, said receivers group including at least one sender for communicating with said senders group;
• said at least one receiver binary distribution tree defining a communication structure having a receiver internal node with a first branch and a second branch depending therefrom, each of said branches including a first member assigned to a corresponding leaf node, said first member being associated with a key association group including at least one other member;
• said receivers group first member including;
• a unique binary ID associated with the corresponding leaf node to which the receivers group first member is assigned;
• a first secret key operable for encrypting data;
• and
• a blinded key derived from said first secret key for exchanging with a blinded key of the other receivers group member;
• wherein, each of said senders is one of said senders group first members and one of said receivers group first members, said sender uses the blinded key of the other receivers group member and the first secret key of the sender to calculate an unblinded key of the receiver internal node to be used for encrypting and decrypting receivers group data that is communicated between said receivers group members located on branches depending from the receiver internal node.