Hardware dependencies and restrictions

6.18 LPAR mode z/VM guest KVM guest

The cryptographic operations that can be accelerated by hardware implementations depend on your IBM Z® hardware and mode of operating the kernel.

The following table provides an overview of the supported cryptographic standards and the earliest mainframe with hardware-acceleration for the associated operations:

Table 1. Hardware prerequisites
Algorithms for	Hardware-acceleration available as of
SHA-1	Available for all supported hardware
SHA-256	Available for all supported hardware
SHA-512	Available for all supported hardware
DES and TDES	ECB and CBC modes Available for all supported hardware: actz196 for the CTR mode
AES	Available for all supported hardware: ECB and CBC modes with 128-bit keys Available for all supported hardware: ECB and CBC modes for all AES key sizes z196 for the CTR mode for all AES key sizes z196 for XTS mode for 256-bit and 512-bit keys z14 for GCM for 128-bit, 192-bit, and 256-bit keys IBM® z17 ™ for "full" XTS keys
GHASH	z196
PAES	z196 (AES with protected key) modes ECB, CBC, CTR, and XTS
CRC32	z13® for CRC-32 (IEEE 802.3 Ethernet) and CRC-32C (Castagnoli)
ChaCha20	z13
SHA3-256 and SHA3-512	z14. With IBM z17 performance is enhanced for small buffers.
Edwards-curve DSA (Ed25519, Ed448), Elliptic Curve DSA (P-256, P-384, P-521)	z15®
HMAC	As of IBM z17
PHMAC (HMAC with protected key)	As of IBM z17

Linux® kernel 6.18 supports System z10® and later IBM Z hardware.

CPACF dependencies

Hardware-acceleration for DES, TDES, AES, GHASH, PAES, SHA, HMAC, and PHMAC requires the Central Processor Assist for Cryptographic Function (CPACF). For information about enabling CPACF, see the documentation for your IBM Z hardware.

Vector Extension Facility dependencies

Hardware-acceleration for CRC32 algorithms and for the ChaCha20 stream cipher requires the Vector Extension Facility. Read the features line from /proc/cpuinfo to find out whether this facility is available on your hardware.

Example:

# grep features /proc/cpuinfo
features        : esan3 zarch stfle msa ldisp eimm dfp edat etf3eh highgprs te vx sie

In the output line, vx indicates that the Vector Extension Facility is available.

FIPS restrictions of the hardware capabilities

If the kernel runs in Federal Information Processing Standard (FIPS) mode, only FIPS 140-2 approved algorithms are available. DES, for example, is not approved by FIPS 140-2.

Read /proc/sys/crypto/fips_enabled to find out whether your kernel runs in FIPS mode.

Example:

# cat /proc/sys/crypto/fips_enabled
1

The kernel of the example runs in FIPS mode. If /proc/sys/crypto/fips_enabled does not exist or the value is other than 1, the kernel does not run in FIPS mode.

You control the FIPS mode with the fips kernel parameter.

For more information about FIPS, see csrc.nist.gov/publications/detail/fips/140/2/final.