SM4EKEY

SM4 key

This instruction takes an input as a 128-bit vector from the first source SIMD&FP register and a 128-bit constant from the second SIMD&FP register. It derives four iterations of the output key, in accordance with the SM4 standard, returning the 128-bit result to the destination SIMD&FP register.

Encoding: Advanced SIMD

Variants: FEAT_SM4 (ARMv8.2)

31	30	29	28	27	26	25	24	23	22	21	20	19	18	17	16	15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
1	1	0	0	1	1	1	0	0	1	1						1	1	0	0	1	0
											Rm						O			opcode		Rn					Rd

SM4EKEY <Vd>.4S, <Vn>.4S, <Vm>.4S

Decoding algorithm

if !IsFeatureImplemented(FEAT_SM4) then EndOfDecode(Decode_UNDEF);
constant integer d = UInt(Rd);
constant integer n = UInt(Rn);
constant integer m = UInt(Rm);

Operation

AArch64.CheckFPAdvSIMDEnabled();

constant bits(128) Vm = V[m, 128];
bits(32) intval;
bits(32) const;
bits(128) roundresult;

roundresult = V[n, 128];
for index = 0 to 3
    const = Elem[Vm, index, 32];

    intval = roundresult<127:96> EOR roundresult<95:64> EOR roundresult<63:32> EOR const;

    for i = 0 to 3
        Elem[intval, i, 8] = Sbox(Elem[intval, i, 8]);

    intval = intval EOR ROL(intval, 13) EOR ROL(intval, 23);
    intval = intval EOR roundresult<31:0>;

    roundresult<31:0>   = roundresult<63:32>;
    roundresult<63:32>  = roundresult<95:64>;
    roundresult<95:64>  = roundresult<127:96>;
    roundresult<127:96> = intval;

V[d, 128] = roundresult;

Explanations

<Vd>: Is the name of the SIMD&FP destination register, encoded in the "Rd" field.
<Vn>: Is the name of the first SIMD&FP source register, encoded in the "Rn" field.
<Vm>: Is the name of the second SIMD&FP source register, encoded in the "Rm" field.

Operational Notes

If PSTATE.DIT is 1:

• The execution time of this instruction is independent of:
  • The values of the data supplied in any of its registers.
  • The values of the NZCV flags.
• The response of this instruction to asynchronous exceptions does not vary based on:
  • The values of the data supplied in any of its registers.
  • The values of the NZCV flags.