SYSTEM AND METHOD FOR SECURING PRIVATE KEYS ISSUED FROM DISTRIBUTED PRIVATE KEY GENERATOR (D-PKG) NODES

• US 20130191632A1
• Filed: 01/24/2013
• Published: 07/25/2013
• Est. Priority Date: 01/25/2012
• Status: Active Grant

• Current Assignee: Omlis Limited
• Original Assignee: Miracl Ltd.
• Inventors: Spector, Brian P., Scott, Michael, Meyers, Gene
• Granted Patent: US 9,065,637 B2
• Time in Patent Office: Days
• US Class Current: 713/155
• CPC Class Codes: H04L 9/083 involving central third party, e.g. key distribution center [KDC] or trusted third party [TTP]
• CPC Class Codes: H04L 9/0847 involving identity based encryption [IBE] schemes
• CPC Class Codes: H04L 9/085 Secret sharing or secret splitting, e.g. threshold schemes
• CPC Class Codes: H04L 9/3073 involving pairings, e.g. identity based encryption [IBE], bilinear mappings or bilinear pairings, e.g. Weil or Tate pairing

Abstract

A system and method where the “dealer” of a split Master Secret becomes the Master Key Server, whose role is to initially compute the Master Secret, create and distribute shares of the Master Secret to two Distributed Private Key Generators (D-PKG), initialize and route the inter-process communication between the nodes, co-ordinate and computationally participate in the User System'"'"'s IBE Private Key generation process.

Claims

1. A method comprising:

selecting a value for x of 2 to q-1;

at a Master Key Server, extracting D-PKG IBE Private Keys;

issuing the IBE Private Keys to the D-PKG nodes;

at the D-PKG nodes, storing their IBE Private Keys;

generating a straight line f(X)=mX+x, where m (the slope) is chosen at random;

dividing x into 3 shares, x₁, x₂ and x₃;

using a different m, breaking a random value r into three shares, r₁, r₂ and r₃;

at the Master Key Server, distributing to the two D-PKG nodes x₂ and r₂ to

one D-PKG node and x₃ and r₃ to another D-PKG, keeping x₁ and r₁ for itself.

2. The method of claim 1 further comprising:

at the Master Key Server, generating a request to Authentication System to enroll the D-PKG nodes in the Authentication System Directory;

at the Master Key Server, applying an HMAC signature to the request;

at the Master Key Server, sending the request to the Authentication Service at the Authentication Service, verifying the HMAC signature of the request;

at the Authentication Service, contacting both DPK-G nodes and Master Key Server with a request for shares of the Master Public Key

at the Master Key Server and D-PKG nodes, calculating R_i=x_iP₁ and pass this to the Authentication System as a response

at the Authentication System, combining shares to obtain the Master Public Key;

R=3R₁−

3R₂+R₃

at the Authentication System, recording the location of the Distributed Private Key Generators, and the Master Public Key into the Authentication System Directory.

3. The method of claim 2, further comprising:

at a User System, initiating an authenticated key agreement protocol with the Authentication System to verify its identity;

creating a session key available to both the User System and Authentication System;

obtaining from the Authentication System Directory the User System Id'"'"'s associated Distributed Private Key Generator nodes and their network addresses;

at the Authentication System, encapsulating the Session Key using the Master Public Key of the nodes and their network addresses as input, resulting in two encapsulated Session Keys, one for each node;

at the Authentication System, creating a request for the Distributed Private Key Generator nodes to issues the specific User System'"'"'s IBE Private Key Shares to the User System;

at the Authentication System, sending the request to both Distributed Private Key Generator nodes;

at the Distributed Private Key Generator nodes, upon receipt of the requests, verifying the HMAC signature;

de-encapsulating their respective Session Keys using their D-PKG IBE Private Keys issued from the Master Key Server;

generating the Private Key Shares using the User System Id as input and encrypt the shares using the Session Key;

the User System, decrypting the shares with the Session Key, and re-assembling the shares by calculating S=2S₁−

S₂.

4. The method of claim 3, further comprising:

performing the calculations of z=x+ID as z_i=x_i+ID in order to calculate s_i=z_ir_i

sending a request with an HMAC signature to the Master Key Server to perform the same calculation;

at the Master Key Server performing the calculation to obtain s_i, choosing a random line equation and calculating three shares in s_i, namely s_i1 s_i2 and s_i3;

at the Master Key Server, keeping S_i, and distributing 5_i2 and 5_i3 to the other two D-PKG nodes, again with an HMAC signature;

at the Master Key Server, calculating its share of S_i as s_i=3s_1i−

3s_2i+s_3i;

at the DPK-G nodes, verifying the HMAC signature and calculating their share of Si as S_i=3s_1i−

3s_2i+s_3i;

distributing all shares of S_i between all nodes and the Master Key Server upon HMAC signature verification, at the D-PKG nodes recovering s=3s₁−

3s₂+s₃;

at the PKG nodes, calculating w_i=r_i/s and computing S₁=w_iP₁ to generate the shares they will serve to the User System;

at the D-PKG nodes, encrypting their shares with the Session Key and distributing the shares to the User System.

5. The method of claim 4, further comprising:

authenticated the user system to a Target System through the Authentication System and is provided access to the Target System;

at the User System, programmatically creating the User System'"'"'s Asymmetric public/private key pair;

creating the User System'"'"'s Symmetric Encryption Key by prompting for a pass phrase where the User System takes the input and calculating the Symmetric Encryption Key using a derivation protocol such as PBKDF2;

at the User System, employing the User System'"'"'s Asymmetric Public Key to encrypt the User System'"'"'s IBE Private Keys;

at the User System, encrypting the User System'"'"'s Asymmetric Private Key with the User System'"'"'s Symmetric Encryption Key derived from the pass phrase;

at the User System, programmatically uploading to the Target System all keys except the User System'"'"'s Symmetric Encryption Key derived from the pass phrase;

securely removing the User System'"'"'s Symmetric Encryption Key derived from the pass phrase is from the User System'"'"'s memory;

at the Target System, making available to the Authentication System the User System'"'"'s Asymmetric Public Key over a communication channel;

at the Authentication System, receiving the User System'"'"'s Asymmetric Public Key, and writing the key into an associate record corresponding to the User System'"'"'s Id in the Authentication System Directory.

6. The method of claim 5, further comprising:

authenticating the user system to Target System through the Authentication System and is provided access to the Target System;

at the User System, making an authenticated request to the Target System to make available all archived User System'"'"'s IBE Private Keys;

at the Target System, responding with the User System'"'"'s archive IBE Private Keys;

at the User System, prompting to enter a pass phrase;

re-constituting the User System'"'"'s Symmetric Encryption Key via a password derivation function;

using the User System'"'"'s Symmetric Encryption Key to decrypt the User System'"'"'s Asymmetric Private Key;

decrypting the archived User System'"'"'s IBE Private Keys that have been encrypted with the User System'"'"'s Asymmetric Public Key are with the User System'"'"'s Asymmetric Private Key.

7. The method of claim 6, further comprising:

at the distributed Key Generator nodes, generating the User System'"'"'s IBE Private Key Shares for the current time period;

at the Distributed Key Generator nodes making an authenticated request to the Authentication System with an HMAC signature to lookup the User System'"'"'s Asymmetric Public Key in the Authentication Service Directory;

at the Authentication Service verifying the signature, performs the lookup, and returns a response including the public key with an HMAC signature;

at the Distributed Private Key Generator nodes verifying the response'"'"'s HMAC signature, and encrypting the User System'"'"'s IBE Private Key Shares with the User System'"'"'s Asymmetric Public Key and removing the key from memory;

at the Distributed Private Key Generator nodes creating a message over a store and forward mechanism such as SMTP and sending the encrypted User System'"'"'s IBE Private Key Shares over email.

8. The method of claim 7, further comprising:

at the distributed Private Key Generator nodes optionally uploading the encrypted User System'"'"'s IBE Private Key Shares into an online storage locker accessible to the User System, or even the Target System;

at the User System, employing the User System'"'"'s Asymmetric Private Key to decrypt the shares.