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Currently, the standalone GHASH code is coupled with crypto_shash. This
has resulted in unnecessary complexity and overhead, as well as the code
being unavailable to library code such as the AES-GCM library. Like was
done with POLYVAL, it needs to find a new home in lib/crypto/.
GHASH and POLYVAL are closely related and can each be implemented in
terms of each other. Optimized code for one can be reused with the
other. But also since GHASH tends to be difficult to implement directly
due to its unnatural bit order, most modern GHASH implementations
(including the existing arm, arm64, powerpc, and x86 optimized GHASH
code, and the new generic GHASH code I'll be adding) actually
reinterpret the GHASH computation as an equivalent POLYVAL computation,
pre and post-processing the inputs and outputs to map to/from POLYVAL.
Given this close relationship, it makes sense to group the GHASH and
POLYVAL code together in the same module. This gives us a wide range of
options for implementing them, reusing code between the two and properly
utilizing whatever instructions each architecture provides.
Thus, GHASH support will be added to the library module that is
currently called "polyval". Rename it to an appropriate name:
"gf128hash". Rename files, options, functions, etc. where appropriate
to reflect the upcoming sharing with GHASH. (Note: polyval_kunit is not
renamed, as ghash_kunit will be added alongside it instead.)
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20260319061723.1140720-2-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
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Add support for POLYVAL to lib/crypto/.
This will replace the polyval crypto_shash algorithm and its use in the
hctr2 template, simplifying the code and reducing overhead.
Specifically, this commit introduces the POLYVAL library API and a
generic implementation of it. Later commits will migrate the existing
architecture-optimized implementations of POLYVAL into lib/crypto/ and
add a KUnit test suite.
I've also rewritten the generic implementation completely, using a more
modern approach instead of the traditional table-based approach. It's
now constant-time, requires no precomputation or dynamic memory
allocations, decreases the per-key memory usage from 4096 bytes to 16
bytes, and is faster than the old polyval-generic even on bulk data
reusing the same key (at least on x86_64, where I measured 15% faster).
We should do this for GHASH too, but for now just do it for POLYVAL.
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Tested-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20251109234726.638437-3-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
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