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authorEric Biggers <ebiggers@google.com>2022-12-01 20:14:52 +0100
committerEric Biggers <ebiggers@google.com>2022-12-02 19:43:00 +0100
commit41952551acb405080726aa38a8a7ce317d9de4bb (patch)
tree669ae17c6bdb13438008e2c8efad5fe00a73c8db /Documentation/filesystems/fscrypt.rst
parentfscrypt: remove unused Speck definitions (diff)
downloadlinux-41952551acb405080726aa38a8a7ce317d9de4bb.tar.xz
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fscrypt: add additional documentation for SM4 support
Add a paragraph about SM4, like there is for the other modes. Signed-off-by: Eric Biggers <ebiggers@google.com> Reviewed-by: Tianjia Zhang <tianjia.zhang@linux.alibaba.com> Link: https://lore.kernel.org/r/20221201191452.6557-1-ebiggers@kernel.org
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diff --git a/Documentation/filesystems/fscrypt.rst b/Documentation/filesystems/fscrypt.rst
index c0784ec05553..ef183387da20 100644
--- a/Documentation/filesystems/fscrypt.rst
+++ b/Documentation/filesystems/fscrypt.rst
@@ -370,6 +370,12 @@ CONFIG_CRYPTO_HCTR2 must be enabled. Also, fast implementations of XCTR and
POLYVAL should be enabled, e.g. CRYPTO_POLYVAL_ARM64_CE and
CRYPTO_AES_ARM64_CE_BLK for ARM64.
+SM4 is a Chinese block cipher that is an alternative to AES. It has
+not seen as much security review as AES, and it only has a 128-bit key
+size. It may be useful in cases where its use is mandated.
+Otherwise, it should not be used. For SM4 support to be available, it
+also needs to be enabled in the kernel crypto API.
+
New encryption modes can be added relatively easily, without changes
to individual filesystems. However, authenticated encryption (AE)
modes are not currently supported because of the difficulty of dealing