AES-NI stands for Advanced Encryption Standard New Instructions, an extension initially proposed by Intel in 2008 for speeding up AES algorithm implementations.

The following code checks whether AES-NI is supported by the CPU:

mov   eax, 1        ; CPUID request code #1
cpuid
test ecx, 1 shl 25  ; Check bit 25
jz not_supported    ; If bit 25 is not set - CPU does not support AES-NI

Instructions in this extension are rather simple and few:

• AESENC: This performs one round of AES encryption on 128-bit data using a 128-bit round key for all encryption rounds except the last round
• AESENCLAST: This performs the last round of AES encryption on 128-bit data
• AESDEC: This performs one round of AES decryption on 128-bit data using a 128-bit round key for all decryption rounds except the last round
• AESDECLAST: This performs the last round of AES decryption on 128-bit data
• AESKEYGENASSIST: This assists in the generation of an AES round key using an 8-bit round constant (RCON)
• AESIMC: This performs the inverse mix column transformation on a 128-bit round key