Cipher mode considerations

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The cryptographic algorithm used by the infrastructure for protected volume encryption is called PAES cipher and is implemented by the paes_s390 kernel module. When you format a volume using LUKS2, you need to specify this PAES cipher together with a block cipher mode of your choice.

The PAES cipher supports the following block cipher modes:

xts: XTS: XEX-based tweaked-codebook mode with ciphertext stealing.
cbc: CBC: Cipher Block Chaining
ctr: CTR: Counter mode
ecb: ECB: Electronic Codebook

Important: In the infrastructure for protected volume encryption, only use the XTS cipher mode. This XEX-based tweaked-codebook mode with ciphertext stealing (XTS) is the block cipher mode recommended by the NIST to encrypt data at-rest. In this mode, the plaintext blocks are XOR-ed with the previous ciphertext block before being encrypted by the block cipher. And in contrast to CBC, it is not vulnerable against code injection attacks.

Restriction: The ESSIV (encrypted sector salt initial vector) mode to generate initialization vectors cannot be used with cryptsetup and the PAES cipher.