[openssl-dev] [openssl.org #3850] [PATCH] Improved performance Multi Block CBC-SHA1 and CBC-SHA256

[Gueron, Shay via RT]

Hello all,

This patch is a contribution to OpenSSL.

It concerns the Multi Block (MB) CBC SHA1/SHA256 implementations
(the function "tls1_1_multi_block_encrypt" in "e_aes_cbc_hmac_sha1.c"
and "e_aes_cbc_hmac_sha256.c").

The patch addresses a slow derivation of the multiple random IV's for the CBC encryption
(~12,000 Cycles on architecture Codename Haswell (HSW),
11,500 Cycles on architecture Codename Broadwell (BDW) ).
This multiple IV's derivation impacts the performance gains from the parallelized encryption (and hashing).

The new code extracts (only) 16 bytes with a Rand-bytes invocation, which are used as an auxiliary key,
and then generates the required number of pseudorandom IV's by applying the decryption primitive.

The effect is speedup on multi-block aes-128-cbc-hmac-sha*, and it is more pronounced for the shorter buffers
(8192 bytes is the shortest length reported by openssl speed utility).

Results: speedup (patch over current) for 8192 bytes size block

                CBC-SHA1            CBC-SHA256
HSW:      1.59x                    1.36x
BDW:      1.53x                    1.33x


Developers and authors:
***************************************************************************
Shay Gueron (1, 2), Regev Shemy (2), Tal Uliel (2)
(1) University of Haifa, Israel
(2) Intel Corporation, Israel Development Center, Haifa, Israel
***************************************************************************



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