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fscrypt provides facilities to use different encryption algorithms which are selectable by userspace when setting the encryption policy. Currently, only AES-256-XTS for file contents and AES-256-CBC-CTS for file names are implemented. This is a clear case of kernel offers the mechanism and userspace selects a policy. Similar to what dm-crypt and ecryptfs have. This patch adds support for using AES-128-CBC for file contents and AES-128-CBC-CTS for file name encryption. To mitigate watermarking attacks, IVs are generated using the ESSIV algorithm. While AES-CBC is actually slightly less secure than AES-XTS from a security point of view, there is more widespread hardware support. Using AES-CBC gives us the acceptable performance while still providing a moderate level of security for persistent storage. Especially low-powered embedded devices with crypto accelerators such as CAAM or CESA often only support AES-CBC. Since using AES-CBC over AES-XTS is basically thought of a last resort, we use AES-128-CBC over AES-256-CBC since it has less encryption rounds and yields noticeable better performance starting from a file size of just a few kB. Signed-off-by: Daniel Walter <dwalter@sigma-star.at> [david@sigma-star.at: addressed review comments] Signed-off-by: David Gstir <david@sigma-star.at> Reviewed-by: Eric Biggers <ebiggers@google.com> Signed-off-by: Theodore Ts'o <tytso@mit.edu>
17 lines
442 B
Plaintext
17 lines
442 B
Plaintext
config FS_ENCRYPTION
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tristate "FS Encryption (Per-file encryption)"
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select CRYPTO
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select CRYPTO_AES
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select CRYPTO_CBC
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select CRYPTO_ECB
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select CRYPTO_XTS
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select CRYPTO_CTS
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select CRYPTO_CTR
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select CRYPTO_SHA256
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select KEYS
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help
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Enable encryption of files and directories. This
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feature is similar to ecryptfs, but it is more memory
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efficient since it avoids caching the encrypted and
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decrypted pages in the page cache.
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