System and method for secure end-to-end chat system

• US 9,432,340 B1
• Filed: 09/15/2015
• Issued: 08/30/2016
• Est. Priority Date: 05/07/2015
• Status: Active Grant

• Current Assignee: Bogart Associates, Inc.
• Original Assignee: Bogart Associates
• Inventors: Tutt, Timothy, Sherwood, John Richard
• Primary Examiner(s): Smithers, Matthew
• Application Number:
  US14/854,764
• Time in Patent Office: 350 Days
• US Class Current: 1/1
• CPC Class Codes: H04L 2209/24 Key scheduling, i.e. generating round keys or sub-keys for block encryption
• CPC Class Codes: H04L 2209/72 Signcrypting, i.e. digital signing and encrypting simultaneously
• CPC Class Codes: H04L 63/0428 wherein the data content is protected, e.g. by encrypting or encapsulating the payload
• CPC Class Codes: H04L 63/045 wherein the sending and receiving network entities apply hybrid encryption, i.e. combination of symmetric and asymmetric encryption cryptographic mechanisms or cryptographic arrangements using a plurality of keys or algorithms H04L9/14
• CPC Class Codes: H04L 63/068 using time-dependent keys, e.g. periodically changing keys cryptographic mechanisms or cryptographic arrangements for controlling usage of secret information H04L9/088
• CPC Class Codes: H04L 63/168 above the transport layer
• CPC Class Codes: H04L 67/02 based on web technology, e.g. hypertext transfer protocol [HTTP]
• CPC Class Codes: H04L 9/0841 involving Diffie-Hellman or related key agreement protocols
• CPC Class Codes: H04L 9/0869 involving random numbers or seeds
• CPC Class Codes: H04L 9/3066 involving algebraic varieties, e.g. elliptic or hyper-elliptic curves
• CPC Class Codes: H04L 9/3242 involving keyed hash functions, e.g. message authentication codes [MACs], CBC-MAC or HMAC
• CPC Class Codes: H04L 9/3247 involving digital signatures
• CPC Class Codes: H04L 9/3271 using challenge-response

Abstract

The present invention provides an efficient secure end-to-end messaging system utilizing encrypted ephemeral messages. The method comprises the steps of using a combination of HTTPS for transport security, using symmetric key cryptography with rotating temporary keys for individual message security, and using elliptic curve cryptography for key derivation and message authentication. The key rotation scheme used provides forward secrecy even between messages and perfect forward secrecy between sessions.

Claims

1. A method of securely transferring data during a communications session, comprising:

connecting to a communications server by sending a request over a communications protocol by providing a client id and a server key;

validating the connection by a challenge response sequence;

initiating a communications session by either randomly generating a symmetric key or generating a key based on a user provided passphrase;

broadcasting an encrypted message to a set of communications participants comprising of a randomly generated salt used for calculating the next key for the session;

inviting a new user to the session providing the initial key and an IVec using ECIES and sending a resynchronization message with the new IVec to the group for the new client to participate.

2. The method of claim 1, wherein the challenge response sequence further comprises a random 4-byte string challenge selected by the server to which the client must respond.

3. The method of claim 1, wherein the server continues to validate that the client is valid with every message sent.

4. The method of claim 1, wherein the server will issue challenges to the client at random intervals that the client must respond to.

5. The method of claim 1, wherein the communications device behaves as both a client and a server.