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ENCODEKEY256

Encode 256-Bit Key With Key Locker

stableVMJITAOTinstruction

Encodings

OpcodeInstructionOp/En64-bitCompat/LegacyDescription
F3 0F 38 FB 11:rrr:bbbENCODEKEY256 r32, r32 <XMM0-6>AValidValidWrap a 256-bit AES key from XMM1:XMM0 into a key handle and store it in XMM0--3.

Operand encoding

Each mode is a value of the Op/En column above. It says which field of the encoded instruction carries each operand, in the order they are written, and whether the instruction reads it, writes it or both.

A

  1. modrm.reg escrituraModRM byte, reg field (bits 5-3)
  2. modrm.rm lecturaModRM byte, r/m field (bits 2-0); with the SIB byte and the displacement when the mod field asks for them
  3. XMM0--1 lectura y escritura
  4. XMM2--6 escritura

Measured cost

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Flags named

Description

The ENCODEKEY2561 instruction wraps a 256-bit AES key from the implicit operand XMM1:XMM0 into a key handle that is then stored in the implicit destination operands XMM0-3.

The explicit source operand is a general-purpose register and specifies what handle restrictions should be built into the handle.

The explicit destination operand is populated with information on the source of the key and its attributes. XMM4 through XMM6 are reserved for future usages and software should not rely upon them being zeroed.

Operation

ENCODEKEY256
#GP (0) if a reserved bit2 in SRC[31:0] is set
InputKey[255:0] := XMM1:XMM0;
KeyMetadata[2:0] = SRC[2:0];
KeyMetadata[23:3] = 0; // Reserved for future usage
KeyMetadata[27:24] = 1; // KeyType is AES-256 (value of 1)
KeyMetadata[127:28] = 0; // Reserved for future usage

// KeyMetadata is the AAD input and InputKey is the Plaintext input for WrapKey256
Handle[511:0] := WrapKey256(InputKey[255:0], KeyMetadata[127:0], IWKey.Integrity Key[127:0], IWKey.Encryption Key[255:0]);

DEST[0] := IWKey.NoBackup;
DEST[4:1] := IWKey.KeySource[3:0];
DEST[31:5] = 0;
XMM0 := Handle[127:0]; // AAD
XMM1 := Handle[255:128]; // Integrity Tag
XMM2 := Handle[383:256]; // CipherText[127:0]
XMM3 := Handle[511:384]; // CipherText[255:128]

XMM4 := 0; // Reserved for future usage
XMM5 := 0; // Reserved for future usage
XMM6 := 0; // Reserved for future usage

RFLAGS.OF, SF, ZF, AF, PF, CF := 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.

2. SRC[31:3] are currently reserved for future usages. SRC[2], which indicates a no-decrypt restriction, is reserved if
    CPUID.19H:EAX[2] is 0. SRC[1], which indicates a no-encrypt restriction, is reserved if CPUID.19H:EAX[1] is 0. SRC[0], which indicates
    a CPL0-only restriction, is reserved if CPUID.19H:EAX[0] is 0.

Flags affected

All arithmetic flags (OF, SF, ZF, AF, PF, CF) are cleared to 0. Although they are cleared for the currently defined operations, future extensions may report information in the flags.

Intel C/C++ compiler intrinsics

ENCODEKEY256 unsigned int _mm_encodekey256_u32(unsigned int htype, __m128i key_lo, __m128i key_hi, void* h);

Exceptions

Real address mode
#GPIf reserved bit is set in source register value.
#UDIf 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.
#NMIf CR0.TS = 1.
Protected mode
#GPIf reserved bit is set in source register value.
#UDIf 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.
#NMIf CR0.TS = 1.
Virtual-8086 mode
#GPIf reserved bit is set in source register value.
#UDIf 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.
#NMIf CR0.TS = 1.
Compatibility mode
#GPIf reserved bit is set in source register value.
#UDIf 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.
#NMIf CR0.TS = 1.
64-bit mode
#GPIf reserved bit is set in source register value.
#UDIf 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.
#NMIf CR0.TS = 1.

Sources