In-place authentication scheme for securing intra-vehicle communication
In some implementations, a scheme for data communication in an automobile includes generating a cleartext message to be transmitted to a second ECU, generating a pseudo-random counter by applying a pseudorandom function to a counter value that is incremented for each cleartext message generated by the ECU; combining the cleartext message and the pseudo-random counter to create a randomized message; selecting from a plurality of available cryptography techniques, a selected cryptography technique; applying to the randomized message, the selected cryptography technique to create a ciphertext; and transmitting to the second ECU over the CAN bus, the ciphertext.
1. A method to authenticate communication over an in-vehicle communications network using in-place cryptography and authentication to more effectively and efficiently obfuscate network traffic from unintended recipients, the method comprising:
listening, at a first electronic control unit (ECU), for a ciphertext having a particular identifier; and
based on receiving a ciphertext from a second ECU having the particular identifier:
identifying a predetermined model corresponding to a particular type of message associated with the ciphertext,
applying one or more block ciphers to the ciphertext to generate a combined value based on the predetermined model,
accessing a counter maintained on the first ECU for the particular type of message,
generating a local reproducible value from the counter, and
performing a logical operation on the local reproducible value and the combined value to generate a cleartext.
2. The method of claim 1 , wherein the predetermined model is generated in a secure environment using an analysis of the second ECU and the cleartext.
3. The method of claim 2 , wherein the analysis includes one or more of static analysis, dynamic analysis, or machine learning.
4. The method of claim 1 , further comprising generating the ciphertext from a cleartext having redundant and non-redundant bits, such that the ciphertext contains no more bits than the cleartext.
5. The method of claim 4 , further comprising:
generating expected values for the redundant bits in the received ciphertext using the predetermined model; and
authenticating the received message by comparing the expected values to redundant bits of the generated cleartext.
6. The method of claim 5 , wherein the authenticating further comprises incrementing a pseudo-random counter and regenerating the cleartext.
7. The method of claim 5 , further comprising identifying the redundant bits of the cleartext based on a presence of one or more patterns of values of bits in the cleartext.
8. The method of claim 1 , wherein the cleartext is generated, in part, by performing a logical operation on the ciphertext using a value derived from the counter, the counter's value being incremented for messages of the particular type that are transmitted over the in-vehicle communications network.
9. The method of claim 5 , wherein the authenticating comprises one or more redundancies not being identified within the cleartext.
10. The method of claim 9 , wherein the authenticating further comprises regenerating the cleartext from the ciphertext using one or more modifications in response to the one or more redundancies not being identified within the cleartext.
11. The method of claim 10 , the cleartext is generated from the ciphertext, in part, by performing a logical operation on the ciphertext using a value derived from the counter, and wherein the cleartext is regenerated by modifying the value of the counter.
12. The method of claim 11 , wherein the logical operation includes an XOR operation.
13. The method of claim 11 , wherein the value is derived from the counter by taking a hash of the counter or applying one or more pseudo-random functions (PRF) to the counter.
14. The method of claim 11 , wherein the counter is incremented for each instance of the cleartext being regenerated, and
wherein the cleartext is regenerated a first threshold number of times, and
after unsuccessfully attempting authenticate the message a second threshold number of times, the first ECU discards the message.
15. The method of claim 14 , further comprising generating an alert in response to unsuccessfully attempting to authenticate the message the second threshold number of times.
16. The method of claim 14 , further comprising generating an alert in response to at least a threshold number of messages from the second ECU over a period of time being unsuccessfully authenticated.
17. The method of claim 1 , wherein the ciphertext received from the second ECU is generated by:
accessing the counter;
generating a reproducible value from the counter;
performing a logical operation on the reproducible value and the cleartext to generate a combined value; and
applying one or more block ciphers to the combined value to generate the ciphertext.
18. The method of claim 1 , wherein the in-vehicle communications network comprises a CAN bus.
19. The method of claim 18 , wherein the first ECU, the second ECU, and the CAN bus are part of an automobile.
20. A system for authenticating communication over an in-vehicle communications network using in-place cryptography and authentication to more effectively and efficiently obfuscate network traffic from unintended recipients, the system comprising:
a first ECU configured to transmit a ciphertext; and
a second ECU configured to:
listen for a ciphertext having a particular identifier; and
based on receiving a ciphertext from the first ECU having the particular identifier:
identify a predetermined model corresponding to a particular type of message associated with the ciphertext,
apply one or more block ciphers to the ciphertext to generate the combined value based on the predetermined model,
access a counter maintained on a second ECU for the particular type of message,
generate a local reproducible value from the counter, and
perform a logical operation on the local reproducible value and the combined value to generate a cleartext.
21. A non-transitory computer-readable medium comprising instructions that, when executed by one or more processors, cause the processor to perform operations to more effectively and efficiently obfuscate network traffic from unintended recipients, the operations comprising:
listening, at a first ECU, for a ciphertext having a particular identifier; and
based on receiving a ciphertext from a second ECU having the particular identifier:
identifying a predetermined model corresponding to a particular type of message associated with the ciphertext,
applying one or more block ciphers to the ciphertext to generate the combined value based on the predetermined model,
accessing a counter maintained on the first ECU for the particular type of message,
generating a local reproducible value from the counter, and
performing a logical operation on the local reproducible value and the combined value to generate a cleartext.