Protocol and method for client-server mutual authentication using event-based OTP
A method of authenticating and encrypting a client-server communication is provided. Two one-time passwords (OTP 1 and OTP 2 ) are generated from a cryptographic token. An encryption key (K_ENC) and a MAC key (K_MAC) are generated based on OTP 2 . The client data are prepared and protected using K_ENC and K_MAC. A request message is sent from the client to the server, and contains the protected client data, a cryptographic token identifier and OTP 1 . OTP 1 is validated at the server, and OTP 2 is generated at the server upon successful validation. K_ENC and K_MAC are derived from OTP 2 at the server. The request message is processed and result data is generated. The result data is encrypted using K_ENC and a digest is created using K_MAC. The encrypted result data is sent to the client, and is decrypted using K_ENC and the authenticity of the result data is verified using K_MAC.
1. A method of authenticating and encrypting a client-server communication, comprising steps of:
a) generating a first one-time password (OTP 1 ) and a second one-time password (OTP 2 ) from a cryptographic token;
b) generating an encryption key (K_ENC) and a MAC (Message Authentication Code) key (K_MAC) based on OTP 2 ;
c) preparing and protecting client data using K_ENC and K_MAC;
d) sending a request message from the client to the server, the request message containing the protected client data, a cryptographic token identifier (TID) and OTP 1 ;
e) validating OTP 1 at the server, and generating OTP 2 at the server upon successful validation;
f) deriving K_ENC and K_MAC from OTP 2 at the server;
g) processing the request message and generating result data;
h) encrypting the result data using K_ENC and creating a digest using K_MAC;
i) sending the encrypted result data to the client; and
j) decrypting the result data at the client using K_ENC and verifying the authenticity of the result data using K_MAC.
2. The method of claim 1 , wherein said request message further includes client request data encrypted with K_ENC and the method includes an additional step of decrypting the client request data at the server using K_ENC.
3. The method of claim 2 , wherein said request message further includes MAC data encrypted with K_MAC and the method includes an additional step of authenticating the client request data using K_MAC.
4. The method of claim 1 , wherein the step of validating OTP 1 takes place internally at the server.
5. The method of claim 1 , wherein the step of validating OTP 1 takes place at a validation service external to the server.
6. The method of claim 1 , wherein K_ENC and K_MAC are derived using PKDF2 (Password-Based Key Derivation Function).
7. The method of claim 1 , wherein K_MAC is derived using a SHA-1 (Secure Hash Algorithm) MAC algorithm.
8. The method of claim 1 , wherein OTP 1 and OTP 2 are derived using a HMAC-based (Hashed Message Authentication Code) OTP (One-Time Password) algorithm.
9. A system to authenticate and to encrypt a client-server communication, comprising:
a processor; and
a memory coupled to the processor, the memory comprising a data authentication and encryption protocol executable by the processor, wherein the data authentication and encryption protocol comprises:
a) generating a pair of one-time passwords, OTP 1 and OTP 2 , where OTP 1 is used for user validation and OTP 2 is used for key generation;
b) deriving an encryption key, K_ENC derived from OTP 2 , used to encrypt data; and
c) deriving a MAC key, K_MAC, derived from OTP 2 , used to authenticate encrypted data,
wherein OTP 1 , OTP 2 , K_ENC and K_MAC are derived such that the protocol does not require a public-key infrastructure.
10. The system of claim 9 , wherein K_ENC and K_MAC are derived using PKDF2 (Password-Based Key Derivation Function).