15. MLX5 Crypto Driver

The MLX5 crypto driver library (librte_crypto_mlx5) provides support for Mellanox ConnectX-6 family adapters.

15.1. Overview

The device can provide disk encryption services, allowing data encryption and decryption towards a disk. Having all encryption/decryption operations done in a single device can reduce cost and overheads of the related FIPS certification, as ConnectX-6 is FIPS 140-2 level-2 ready. The encryption cipher is AES-XTS of 256/512 bit key size.

MKEY is a memory region object in the hardware, that holds address translation information and attributes per memory area. Its ID must be tied to addresses provided to the hardware. The encryption operations are performed with MKEY read/write transactions, when the MKEY is configured to perform crypto operations.

The encryption does not require text to be aligned to the AES block size (128b).

For security reasons and to increase robustness, this driver only deals with virtual memory addresses. The way resources allocations are handled by the kernel, combined with hardware specifications that allow handling virtual memory addresses directly, ensure that DPDK applications cannot access random physical memory (or memory that does not belong to the current process).

The PMD uses libibverbs and libmlx5 to access the device firmware or to access the hardware components directly. There are different levels of objects and bypassing abilities. To get the best performances:

  • Verbs is a complete high-level generic API.
  • Direct Verbs is a device-specific API.
  • DevX allows to access firmware objects.

Enabling librte_crypto_mlx5 causes DPDK applications to be linked against libibverbs.

In order to move the device to crypto operational mode, credential and KEK (Key Encrypting Key) should be set as the first step. The credential will be used by the software in order to perform crypto login, and the KEK is the AES Key Wrap Algorithm (rfc3394) key that will be used for sensitive data wrapping. The credential and the AES-XTS keys should be provided to the hardware, as ciphertext encrypted by the KEK.

A keytag (64 bits) should be appended to the AES-XTS keys (before wrapping), and will be validated when the hardware attempts to access it.

When crypto engines are defined to work in wrapped import method, they come out of the factory in Commissioning mode, and thus, cannot be used for crypto operations yet. A dedicated tool is used for changing the mode from Commissioning to Operational, while setting the first import_KEK and credential in plaintext. The mlxreg dedicated tool should be used as follows:

  • Set CRYPTO_OPERATIONAL register to set the device in crypto operational mode.

    The input to this tool is:

    • The first credential in plaintext, 40B.
    • The first import_KEK in plaintext: kek size 0 for 16B or 1 for 32B, kek data.


    mlxreg -d /dev/mst/mt4123_pciconf0 --reg_name CRYPTO_OPERATIONAL --get

    The “wrapped_crypto_operational” value will be “0x00000000”. The command to set the register should be executed only once, and all the values mentioned above should be specified in the same command.


    mlxreg -d /dev/mst/mt4123_pciconf0 --reg_name CRYPTO_OPERATIONAL \
    --set "credential[0]=0x10000000, credential[1]=0x10000000, kek[0]=0x00000000"

    All values not specified will remain 0. “wrapped_crypto_going_to_commissioning” and “wrapped_crypto_operational” should not be specified.

    All the device ports should set it in order to move to operational mode.

  • Query CRYPTO_OPERATIONAL register to make sure the device is in Operational mode.


    mlxreg -d /dev/mst/mt4123_pciconf0 --reg_name CRYPTO_OPERATIONAL --get

    The “wrapped_crypto_operational” value will be “0x00000001” if the mode was successfully changed to operational mode.

    The mlx5 crypto PMD can be verified by running the test application:

    dpdk-test -c 1 -n 1 -w <dev>,class=crypto,wcs_file=<file_path>

15.2. Driver options

  • class parameter [string]

    Select the class of the driver that should probe the device. crypto for the mlx5 crypto driver.

  • wcs_file parameter [string] - mandatory

    File path including only the wrapped credential in string format of hexadecimal numbers, represent 48 bytes (8 bytes IV added by the AES key wrap algorithm).

  • import_kek_id parameter [int]

    The identifier of the KEK, default value is 0 represents the operational register import_kek..

  • credential_id parameter [int]

    The identifier of the credential, default value is 0 represents the operational register credential.

  • keytag parameter [int]

    The plaintext of the keytag appended to the AES-XTS keys, default value is 0.

  • max_segs_num parameter [int]

    Maximum number of mbuf chain segments(src or dest), default value is 8.

15.3. Supported NICs

  • Mellanox® ConnectX®-6 200G MCX654106A-HCAT (2x200G)

15.4. Limitations

  • AES-XTS keys provided in xform must include keytag and should be wrapped.
  • The supported data-unit lengths are 512B and 1KB. In case the dataunit_len is not provided in the cipher xform, the OP length is limited to the above values and 1MB.

15.5. Prerequisites