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-rw-r--r--Documentation/filesystems/fscrypt.rst7
1 files changed, 7 insertions, 0 deletions
diff --git a/Documentation/filesystems/fscrypt.rst b/Documentation/filesystems/fscrypt.rst
index 5ba5817c17c2..ef183387da20 100644
--- a/Documentation/filesystems/fscrypt.rst
+++ b/Documentation/filesystems/fscrypt.rst
@@ -338,6 +338,7 @@ Currently, the following pairs of encryption modes are supported:
- AES-128-CBC for contents and AES-128-CTS-CBC for filenames
- Adiantum for both contents and filenames
- AES-256-XTS for contents and AES-256-HCTR2 for filenames (v2 policies only)
+- SM4-XTS for contents and SM4-CTS-CBC for filenames (v2 policies only)
If unsure, you should use the (AES-256-XTS, AES-256-CTS-CBC) pair.
@@ -369,6 +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