Скорость OpenSSL AES отличается с EVP и без AES-NI

Question

Мой компьютер не имеет AES-NI, но когда я запускаю openssl speed с и без -evp я вижу разницу в скорости. Почему это?

openssl speed aes-128-cbc
Doing aes-128 cbc for 3s on 16 size blocks: 18132001 aes-128 cbc's in 3.00s
Doing aes-128 cbc for 3s on 64 size blocks: 4890318 aes-128 cbc's in 3.00s
Doing aes-128 cbc for 3s on 256 size blocks: 1246069 aes-128 cbc's in 3.00s
Doing aes-128 cbc for 3s on 1024 size blocks: 311859 aes-128 cbc's in 3.00s
Doing aes-128 cbc for 3s on 8192 size blocks: 38970 aes-128 cbc's in 3.00s
OpenSSL 1.0.1f 6 Jan 2014
built on: Thu Jun 11 15:30:15 UTC 2015
options:bn(64,64) rc4(16x,int) des(idx,cisc,16,int) aes(partial) blowfish(idx) 
compiler: cc -fPIC -DOPENSSL_PIC -DOPENSSL_THREADS -D_REENTRANT -DDSO_DLFCN -DHAVE_DLFCN_H -m64 -DL_ENDIAN -DTERMIO -g -O2 -fstack-protector-strong -Wformat -Werror=format-security -D_FORTIFY_SOURCE=2 -Wl,-Bsymbolic-functions -Wl,-z,relro -Wa,--noexecstack -Wall -DMD32_REG_T=int -DOPENSSL_IA32_SSE2 -DOPENSSL_BN_ASM_MONT -DOPENSSL_BN_ASM_MONT5 -DOPENSSL_BN_ASM_GF2m -DSHA1_ASM -DSHA256_ASM -DSHA512_ASM -DMD5_ASM -DAES_ASM -DVPAES_ASM -DBSAES_ASM -DWHIRLPOOL_ASM -DGHASH_ASM
The 'numbers' are in 1000s of bytes per second processed.
type             16 bytes     64 bytes    256 bytes   1024 bytes   8192 bytes
aes-128 cbc      96704.01k   104326.78k   106331.22k   106447.87k   106414.08k

А также

openssl speed -evp aes-128-cbc
Doing aes-128-cbc for 3s on 16 size blocks: 90633962 aes-128-cbc's in 2.99s
Doing aes-128-cbc for 3s on 64 size blocks: 24880226 aes-128-cbc's in 3.00s
Doing aes-128-cbc for 3s on 256 size blocks: 7574778 aes-128-cbc's in 3.00s
Doing aes-128-cbc for 3s on 1024 size blocks: 1962765 aes-128-cbc's in 3.00s
Doing aes-128-cbc for 3s on 8192 size blocks: 247920 aes-128-cbc's in 2.99s
OpenSSL 1.0.1f 6 Jan 2014
built on: Thu Jun 11 15:28:12 UTC 2015
options:bn(64,64) rc4(8x,int) des(idx,cisc,16,int) aes(partial) blowfish(idx) 
compiler: cc -fPIC -DOPENSSL_PIC -DOPENSSL_THREADS -D_REENTRANT -DDSO_DLFCN -DHAVE_DLFCN_H -m64 -DL_ENDIAN -DTERMIO -g -O2 -fstack-protector --param=ssp-buffer-size=4 -Wformat -Werror=format-security -D_FORTIFY_SOURCE=2 -Wl,-Bsymbolic-functions -Wl,-z,relro -Wa,--noexecstack -Wall -DMD32_REG_T=int -DOPENSSL_IA32_SSE2 -DOPENSSL_BN_ASM_MONT -DOPENSSL_BN_ASM_MONT5 -DOPENSSL_BN_ASM_GF2m -DSHA1_ASM -DSHA256_ASM -DSHA512_ASM -DMD5_ASM -DAES_ASM -DVPAES_ASM -DBSAES_ASM -DWHIRLPOOL_ASM -DGHASH_ASM
The 'numbers' are in 1000s of bytes per second processed.
type             16 bytes     64 bytes    256 bytes   1024 bytes   8192 bytes
aes-128-cbc     484997.79k   530778.15k   646381.06k   669957.12k   679251.05k

Answer 1

На самом деле evp контролирует не только AES_NI, но и целую кучу встроенных функций и оптимизаций ЦП, поскольку использует совершенно другую реализацию алгоритма AES, который пытается максимально использовать преимущества аппаратного и компилятора. Этот ответ от security.stackexchange объясняет это гораздо лучше, чем я.