Efficient methods for protecting identity in authenticated transmissions

• US 9,967,090 B2
• Filed: 04/17/2017
• Issued: 05/08/2018
• Est. Priority Date: 01/13/2014
• Status: Active Grant

• Current Assignee: Visa International Service Association (Visa, Inc.)
• Original Assignee: Visa International Service Association (Visa, Inc.)
• Inventors: Le Saint, Eric
• Primary Examiner(s): Hailu, Teshome
• Application Number:
  US15/489,409
• Publication Number:
  US 20170222801A1
• Time in Patent Office: 386 Days
• Field of Search: 713171
• CPC Class Codes: H04L 2209/04 Masking or blinding
• CPC Class Codes: H04L 2209/16 Obfuscation or hiding, e.g. involving white box
• CPC Class Codes: H04L 2209/24 Key scheduling, i.e. generating round keys or sub-keys for block encryption
• CPC Class Codes: H04L 2209/56 Financial cryptography, e.g. electronic payment or e-cash
• CPC Class Codes: H04L 2209/805 Lightweight hardware, e.g. radio-frequency identification [RFID] or sensor
• CPC Class Codes: H04L 63/061 for key exchange, e.g. in peer-to-peer networks cryptographic mechanisms or cryptographic arrangements for key agreement H04L9/0838
• CPC Class Codes: H04L 9/0819 Key transport or distribution, i.e. key establishment techniques where one party creates or otherwise obtains a secret value, and securely transfers it to the other(s) network architectures or network communication protocols for key distribution in a packet data network H04L63/062
• CPC Class Codes: H04L 9/0844 with user authentication or key authentication, e.g. ElGamal, MTI, MQV-Menezes-Qu-Vanstone protocol or Diffie-Hellman protocols using implicitly-certified keys
• CPC Class Codes: H04L 9/14 using a plurality of keys or algorithms
• CPC Class Codes: H04W 12/041 Key generation or derivation

Abstract

Systems and methods are provided for protecting identity in an authenticated data transmission. For example, a contactless transaction between a portable user device and an access device may be conducted without exposing the portable user device'"'"'s public key in cleartext. In one embodiment, an access device may send an access device public key to a portable user device. The user device may return a blinded user device public key and encrypted user device data. The access device may determine a shared secret using the blinded user device public key and an access device private key. The access device may then decrypt the encrypted user device data using the shared secret.

Claims

1. An access device comprising:

a processor; and

a non-transitory computer-readable storage medium comprising code executable by the processor for implementing a method comprising;

sending a request message including an access device public key to a user device, wherein the access device public key is associated with an access device private key;

receiving a response message including a blinded user device public key and encrypted user device data from the user device, the response message being received in response to the sending of the request message, wherein the blinded user device public key is generated by the user device obfuscating a user device public key using a cryptographic nonce, the cryptographic nonce being a randomly generated value or a pseudo-randomly generated value, and wherein the encrypted user device data is encrypted by the user device using a shared secret, the shared secret being different from the cryptographic nonce; and

generating the shared secret using the access device private key associated with the access device public key that is included in the request message and using the blinded user device public key; and

decrypting the encrypted user device data using the shared secret.

2. The access device of claim 1, wherein the generation of the shared secret by the user device is not based on any other keys from the access device besides those included in the request message, and wherein the generating of the shared secret by the access device is not based on any other keys from the user device besides those included in the response message.

3. The access device of claim 1, wherein the access device public key and the access device private key form an ephemeral key pair, the method further comprising deleting the ephemeral key pair after the generating of the shared secret.

4. The access device of claim 1, wherein decrypting the encrypted user device data using the shared secret comprises generating a session key using the shared secret.

5. The access device of claim 1, wherein the user device data comprises a user device certificate comprising a user device public key and the cryptographic nonce used to generate the blinded user device public key, and wherein the method further comprises:

validating the user device certificate;

generating a second blinded user device public key using the user device public key and the cryptographic nonce; and

comparing the second blinded user device public key with the received blinded user device public key, wherein the user device is authenticated if the second blinded user device public key matches the received blinded user device public key.

6. The access device of claim 1, wherein the shared secret is a first shared secret, and wherein the method further comprises:

generating a second shared secret using the first shared secret; and

associating the second shared secret with the user device, wherein the second shared secret is used to decrypt subsequent user device data received from the user device.

7. The access device of claim 1, the method further comprising:

conducting a transaction using the user device data.

8. The access device of claim 1, wherein the access device is in a system, the system further comprising:

the user device, wherein the user device is configured to;

receive the access device public key;

generate the shared secret using the access device public key, a user device private key, and the cryptographic nonce;

encrypt user device data using the shared secret; and

send the response message including the encrypted user device data and the blinded user device public key to the access device.

9. The access device of claim 1, wherein the method further comprises:

determining that the user device has entered a contactless field of the access device, wherein the sending of the request message occurs in response to the determining that the user device has entered the contactless field of the access device, and wherein the request message is sent via the contactless field.

10. The access device of claim 1, wherein the user device public key and a user device private key form a user device key pair, wherein the user device generates the shared secret using the user device private key, the cryptographic nonce, and the access device public key.

11. The access device of claim 1, wherein the user device public key is included in a certificate for authenticating the user device, the certificate being signed by a certificate authority, and wherein the certificate is included in the encrypted user device data.

12. A computer-implemented method comprising:

sending, by an access device having one or more processors, a request message including an access device public key to a user device, wherein the access device public key is associated with an access device private key;

receiving, by the access device, a response message including a blinded user device public key and encrypted user device data from the user device, the response message being received in response to the sending of the request message, wherein the blinded user device public key is generated by the user device obfuscating a user device public key using a cryptographic nonce, the cryptographic nonce being a randomly generated value or a pseudo-randomly generated value, and wherein the encrypted user device data is encrypted by the user device using a shared secret, the shared secret being different from the cryptographic nonce; and

generating, by the access device, the shared secret using the access device private key associated with the access device public key that is included in the request message and using the blinded user device public key included in the response message, wherein the shared secret is known to the user device.

13. The computer-implemented method of claim 12, wherein the generation of the shared secret by the user device is not based on any other keys from the access device besides those included in the request message, and wherein the generating of the shared secret by the access device is not based on any other keys from the user device besides those included in the response message.

14. The computer-implemented method of claim 12, wherein the access device public key and the access device private key form an ephemeral key pair, wherein the ephemeral key pair is deleted after shared secret is generated.

15. The computer-implemented method of claim 12, further comprising:

generating, by the access device, a session key using the shared secret.

16. The computer-implemented method of claim 15, further comprising:

decrypting, by the access device, the encrypted user device data using the session key to determine user device data.

17. The computer-implemented method of claim 16, wherein the user device data comprises a user device certificate comprising a user device public key and a cryptographic nonce used to generate the blinded user device public key, and wherein the method further comprises:

validating, by the access device, the user device certificate;

generating, by the access device, a second blinded user device public key using the user device public key and the cryptographic nonce; and

comparing, by the access device, the second blinded user device public key with the received blinded user device public key, wherein the user device is authenticated if the second blinded user device public key matches the received blinded user device public key.

18. The computer-implemented method of claim 16, wherein the shared secret is a first shared secret, and wherein the method further comprises:

generating, by the access device, a second shared secret using the first shared secret; and

associating, by the access device, the second shared secret with the user device, wherein the second shared secret is used to decrypt subsequent user device data received from the user device.

19. The computer-implemented method of claim 16, further comprising:

conducting, by the access device, a transaction using the user device data.

20. A computer-implemented method comprising:

receiving, by a user device, a request message including an access device public key from an access device;

generating, by the user device, a cryptographic nonce, the cryptographic nonce being a randomly generated value or a pseudo-randomly generated value;

generating, by the user device, a shared secret using the access device public key included in the request message, a user device private key, and the cryptographic nonce, the shared secret being different from the cryptographic nonce;

generating, by the user device, a blinded user device public key by obfuscating a user device public key using the cryptographic nonce;

encrypting, by the user device, user device data using the shared secret; and

sending, by the user device, a response message including the blinded user device public key and the encrypted user device data to the access device in response to the receiving of the request message, thereby allowing the access device to generate the shared secret using the blinded user device public key and an access device private key corresponding to the access device public key and to decrypt the encrypted user device data using the shared secret.

21. The computer-implemented method of claim 20, wherein the generating of the shared secret by the user device is not based on any other keys from the access device besides those included in the request message, and wherein the generation of the shared secret by the access device is not based on any other keys from the user device besides those included in the response message.

22. The computer-implemented method of claim 20, further comprising:

encrypting, by the user device, user device data using a session key to generate encrypted user device data wherein the user device data comprises a user device certificate, and wherein the access device authenticates the user device using the user device certificate and the cryptographic nonce; and

sending, by the user device, the encrypted user device data to the access device.

23. An user device comprising:

a processor; and

a non-transitory computer-readable storage medium comprising code executable by the processor for implementing a method comprising;

receiving a request message including an access device public key from an access device;

generating a cryptographic nonce, the cryptographic nonce being a randomly generated value or a pseudo-randomly generated value;

generating a shared secret using the access device public key included in the request message, a user device private key, and the cryptographic nonce, the shared secret being different from the cryptographic nonce;

generating a blinded user device public key by obfuscating a user device public key using the cryptographic nonce;

encrypting user device data using the shared secret; and

sending a response message including the blinded user device public key and the encrypted user device data to the access device in response to the receiving of the request message, thereby allowing the access device to generate the shared secret using the blinded user device public key and an access device private key corresponding to the access device public key and to decrypt the encrypted user device data using the shared secret.

24. The user device of claim 23, wherein the generating of the shared secret is not based on any other keys from the access device besides those included in the request message, and wherein the generation of the shared secret by the access device is not based on any other keys from the user device besides those included in the response message.

25. The user device of claim 23, wherein the method further comprises:

encrypting user device data using a session key to generate encrypted user device data wherein the user device data comprises a user device certificate, and wherein the access device authenticates the user device using the user device certificate and the cryptographic nonce; and

sending the encrypted user device data to the access device.