IBM z13s, Technical Manual

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Chapter 6. Cryptography
209
and protected keys can be used. Protected keys require a Crypto Express5S card running in
CCA mode. For more information, see 6.5.2, “Crypto Express5S as a CCA coprocessor” on
page 214.
The hashing algorithm SHA-1, and SHA-2 support for SHA-224, SHA-256, SHA-384, and
SHA-512, are shipped enabled on all servers and do not require the CPACF enablement
feature. For all other algorithms, the no-charge CPACF enablement feature (FC 3863) is
required.
The CPACF functions are supported by z/OS, z/VM, z/VSE, zTPF, and Linux on z Systems.
6.4.2 CPACF protected key
z13s server support the protected key implementation. Since IBM 4764 PCI-X cryptographic
coprocessor (PCIXCC) deployment, secure keys are processed on the PCI-X and PCIe
cards. This process requires an asynchronous operation to move the data and keys from the
general-purpose central processor (CP) to the crypto cards. Clear keys process faster than
secure keys because the process is done synchronously on the CPACF. Protected keys blend
the security of Crypto Express5S coprocessors and the performance characteristics of the
CPACF. This process allows it to run closer to the speed of clear keys.
An enhancement to CPACF facilitates the continued privacy of cryptographic key material
when used for data encryption. In Crypto Express5S coprocessors, a secure key is encrypted
under a master key. However, a protected key is encrypted under a wrapping key that is
unique to each LPAR. Because the wrapping key is unique to each LPAR, a protected key
cannot be shared with another LPAR. By using key wrapping, CPACF ensures that key
material is not visible to applications or operating systems during encryption operations.
CPACF code generates the wrapping key and stores it in the protected area of the hardware
system area (HSA). The wrapping key is accessible only by firmware. It cannot be accessed
by operating systems or applications. DES/T-DES and AES algorithms are implemented in
CPACF code with the support of hardware assist functions. Two variations of wrapping keys
are generated: One for DES/T-DES keys and another for AES keys.