Countering Security Threats | MACsec and Encryption

Encryption Board

Common key cryptography

Symmetric key cryptography is a cryptography method that uses the same key to encrypt and decrypt plaintext. The symmetric key is shared between the sender and receiver, and the plaintext or ciphertext is encrypted or decrypted using the symmetric key. When sending or receiving data between multiple people, a symmetric key is required for each pair of sender and receiver, so the total number of keys increases quadratically.

public key cryptography

Common key cryptography is a cryptography method that uses different keys for encryption and decryption. Plain text encrypted with one key can only be decrypted with the other key, and it is impossible to guess one key from the other. One key is strictly managed as a private key, and the other is made public as a common key. When sending and receiving data between multiple parties, each sender and receiver must have a pair of keys, so the total number of keys increases linearly.

MACsec

principle

The device encrypts the data in FRAMES received by the xMII using a pre-stored common key. The encrypted FRAMES is sent to the link partner by the MDI transmit block. The other device decrypts the encrypted packet received by the MDI using the common key.

• Ethernet FRAMES | Learn about the standard Ethernet FRAMES for sending and receiving data.

• What is MDI? | Learn about the signals sent and received between MDI and the Automotive Ethernet PHY.

• What is xMII? | Learn about MII (Media Independent Interface).

MACsec Use Cases

Consider a use case where data acquired from a camera is sent to the PHY connected to CONNECTORS and processed by the subsystem.
Malicious hackers can attach hacking devices to CONNECTORS, allowing them to eavesdrop on or tamper with data. MACsec is used to prevent this.

Data eavesdropping

The data copied by the hacking device is sent to the hacker, who can then view the same image as the monitor on the subsystem. MACsec encrypts the data with a shared key, so a hacker who does not have the shared key cannot decrypt the copied data. Therefore, the hacker cannot view the same screen as the monitor.

Data tampering

If data sent from a hacker is sent to the monitor through the hacking device, the image will not be displayed correctly. MACsec uses data that is not properly encrypted, so the image will be displayed on the monitor as normal.