x86doc › AESDECWIDE128KL - Perform Ten Rounds of AES Decryption Flow With Key Locker on 8 Blocks Using 128-Bit Key

AESDECWIDE128KL—Perform Ten Rounds of AES Decryption Flow With Key Locker on 8 Blocks Using 128-Bit Key

Opcode/Instruction	Op/En	64/32-bit Mode	CPUID Feature Flag	Description
F3 0F 38 D8 !(11):001:bbb AESDECWIDE128KL m384, <XMM0-7>	A	V/V	AESKLEWIDE_KL	Decrypt XMM0-7 using 128-bit AES key indicated by handle at m384 and store each resultant block back to its corresponding register.

Instruction Operand Encoding

Op/En	Tuple	Operand 1	Operands 2—9
A	N/A	ModRM:r/m (r)	Implicit XMM0-7 (r, w)

Description

The AESDECWIDE128KL¹ instruction performs ten rounds of AES to decrypt each of the eight blocks in XMM0-7 using the 128-bit key indicated by the handle from the second operand. It replaces each input block in XMM0-7 with its corresponding decrypted block if the operation succeeds (e.g., does not run into a handle violation failure).

Operation

AESDECWIDE128KL

Handle := UnalignedLoad of 384 bit (SRC);
                                                    // Load is not guaranteed to be atomic.
Illegal Handle = (HandleReservedBitSet (Handle) ||
                 (Handle[0] AND (CPL > 0)) ||
                 Handle [2] ||
                 HandleKeyType (Handle) != HANDLE_KEY_TYPE_AES128);
IF (Illegal Handle)
    THEN RFLAGS.ZF := 1;
    ELSE
         (UnwrappedKey, Authentic) := UnwrapKeyAndAuthenticate384 (Handle[383:0], IWKey);
         IF Authentic == 0 {
              THEN RFLAGS.ZF := 1;
              ELSE
                    XMM0 := AES128Decrypt (XMM0, UnwrappedKey) ;
                    XMM1 := AES128Decrypt (XMM1, UnwrappedKey) ;
                    XMM2 := AES128Decrypt (XMM2, UnwrappedKey) ;
                    XMM3 := AES128Decrypt (XMM3, UnwrappedKey) ;
                    XMM4 := AES128Decrypt (XMM4, UnwrappedKey) ;
                    XMM5 := AES128Decrypt (XMM5, UnwrappedKey) ;
                    XMM6 := AES128Decrypt (XMM6, UnwrappedKey) ;
                    XMM7 := AES128Decrypt (XMM7, UnwrappedKey) ;
                    RFLAGS.ZF := 0;
         FI;
FI;
RFLAGS.OF, SF, AF, PF, CF := 0;

Flags Affected

ZF is set to 0 if the operation succeeded and set to 1 if the operation failed due to a handle violation. The other arithmetic flags (OF, SF, AF, PF, CF) are cleared to 0.

1.

Further details on Key Locker and usage of this instruction can be found here:

https://software.intel.com/content/www/us/en/develop/download/intel-key-locker-specification.html.

Intel C/C++ Compiler Intrinsic Equivalent

AESDECWIDE128KLunsigned char _mm_aesdecwide128kl_u8(__m128i odata[8], const __m128i idata[8], const void* h);

Exceptions (All Operating Modes)

#UD

If the LOCK prefix is used.

If CPUID.07H:ECX.KL [bit 23] = 0.

If CR4.KL = 0.

If CPUID.19H:EBX.AESKLE [bit 0] = 0.

If CR0.EM = 1.

If CR4.OSFXSR = 0.

If CPUID.19H:EBX.WIDE_KL [bit 2] = 0.

#NM

If CR0.TS = 1.

#PF

If a page fault occurs.

#GP(0)

If a memory operand effective address is outside the CS, DS, ES, FS, or GS segment limit.

If the DS, ES, FS, or GS register is used to access memory and it contains a NULL segment selector.

If the memory address is in a non-canonical form.

#SS(0)

If a memory operand effective address is outside the SS segment limit.

If a memory address referencing the SS segment is in a non-canonical form.