Skip to content


Browse files Browse the repository at this point in the history
ARM: add support for bit sliced AES using NEON instructions
Bit sliced AES gives around 45% speedup on Cortex-A15 for encryption
and around 25% for decryption. This implementation of the AES algorithm
does not rely on any lookup tables so it is believed to be invulnerable
to cache timing attacks.

This algorithm processes up to 8 blocks in parallel in constant time. This
means that it is not usable by chaining modes that are strictly sequential
in nature, such as CBC encryption. CBC decryption, however, can benefit from
this implementation and runs about 25% faster. The other chaining modes
implemented in this module, XTS and CTR, can execute fully in parallel in
both directions.

The core code has been adopted from the OpenSSL project (in collaboration
with the original author, on cc). For ease of maintenance, this version is
identical to the upstream OpenSSL code, i.e., all modifications that were
required to make it suitable for inclusion into the kernel have been made
upstream. The original can be found here:;a=commit;h=6f6a6130

Note to integrators:
While this implementation is significantly faster than the existing table
based ones (generic or ARM asm), especially in CTR mode, the effects on
power efficiency are unclear as of yet. This code does fundamentally more
work, by calculating values that the table based code obtains by a simple
lookup; only by doing all of that work in a SIMD fashion, it manages to
perform better.

Cc: Andy Polyakov <>
Acked-by: Nicolas Pitre <>
Signed-off-by: Ard Biesheuvel <>

  • Loading branch information
Ard Biesheuvel authored and StefanescuCristian committed Jun 4, 2014
1 parent 2d2212c commit 8591fd4
Show file tree
Hide file tree
Showing 5 changed files with 5,504 additions and 0 deletions.
19 changes: 19 additions & 0 deletions arch/arm/crypto/Makefile
@@ -0,0 +1,19 @@
# Arch-specific CryptoAPI modules.

obj-$(CONFIG_CRYPTO_AES_ARM) += aes-arm.o
obj-$(CONFIG_CRYPTO_AES_ARM_BS) += aes-arm-bs.o
obj-$(CONFIG_CRYPTO_SHA1_ARM) += sha1-arm.o

aes-arm-y := aes-armv4.o aes_glue.o
aes-arm-bs-y := aesbs-core.o aesbs-glue.o
sha1-arm-y := sha1-armv4-large.o sha1_glue.o

quiet_cmd_perl = PERL $@
cmd_perl = $(PERL) $(<) > $(@)

$(src)/aesbs-core.S_shipped: $(src)/
$(call cmd,perl)

.PRECIOUS: $(obj)/aesbs-core.S

0 comments on commit 8591fd4

Please sign in to comment.