aesdec128kl

AES Decrypt 128-bit Key Locker

AESDEC128KL m128, xmm

Decrypts data using Key Locker handle.

Details

Performs AES decryption on 128-bit data in the XMM register using a Key Locker handle stored in memory. The decrypted result is written back to the XMM register, and ZF is set to indicate success or failure. This instruction requires KEYLOCKER support and unwraps the key using the internal wrapping key.

Pseudocode Operation

IF CPUID.KEYLOCKER = 0 THEN #UD FI;
handle ← [dest][127:0];
ciphertext ← src[127:0];
plaintext ← AES_DECRYPT_128(ciphertext, UNWRAP_KEY_128(handle, INTERNAL_WRAPPING_KEY));
src[127:0] ← plaintext;
ZF ← 0;

Example

AESDEC128KL [rbp-16], xmm0

Encoding

Binary Layout

Format Legacy

Opcode F3 0F 38 DD !(11):rrr:bbb

Extension KEYLOCKER

Operands

dest
128-bit memory operand
src
128-bit SSE/AVX register (XMM)

Reference (Intel® SDM)

Instruction Forms

Opcode	Instruction	Op/En	64/32-bit Mode	CPUID	Description
F3 0F 38 DD !(11):rrr:bbb	AESDEC128KL xmm, m384	A	V/V	AESKLE	Decrypt xmm using 128-bit AES key indicated by handle at m384 and store result in xmm.

Instruction Operand Encoding

Op/En	Tuple Type	Operand 1	Operand 2	Operand 3	Operand 4
A	N/A	ModRM:reg (r, w)	ModRM:r/m (r)	N/A	N/A

Description

The AESDEC128KL1 instruction performs 10 rounds of AES to decrypt the first operand using the 128-bit key indicated by the handle from the second operand. It stores the result in the first operand if the operation succeeds (e.g., does not run into a handle violation failure).

Operation

AESDEC128KL
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
DEST := AES128Decrypt (DEST, UnwrappedKey) ;
RFLAGS.ZF := 0;
FI;
FI;
RFLAGS.OF, SF, AF, PF, CF := 0;

Intel C/C++ Compiler Intrinsic Equivalent

AESDEC128KL   unsigned char _mm_aesdec128kl_u8(__m128i* odata, __m128i idata, const void* h);
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.
AESDEC128KL—Perform Ten Rounds of AES Decryption Flow With Key Locker Using 128-Bit Key                                             Vol. 2A 3-35
Exceptions (All Operating Modes)
#UD                     If the LOCK prefix is used.
If CPUID.07H.00H:ECX.KEY_LOCKER[23] = 0.
If CR4.KL = 0.
If CPUID.19H:EBX.AESKLE[0] = 0.
If CR0.EM = 1.
If CR4.OSFXSR = 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.
AESDEC128KL—Perform Ten Rounds of AES Decryption Flow With Key Locker Using 128-Bit Key                                             Vol. 2A 3-36

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.