sm4ekey

SM4 Key (A32)

SM4EKEY.32 <Qd>, <Qm>

SM4 key schedule step.

Details

SM4 Key performs one round of SM4 key schedule expansion, computing a derived key from the previous key material. This instruction does not affect condition flags. The instruction is A32-only and requires the Crypto SM4 extension; it generates an Undefined Instruction exception if executed without the extension enabled.

Pseudocode Operation

Qd ← SM4_KeySchedule(Qd, Qm)

Example

SM4EKEY.32 q0, q2

Encoding

Binary Layout
01000101
0
0
1
Zm
11110
0
Zn
Zd
 
Format Crypto 2-Reg
Opcode 0x4520F000
Extension Crypto (SM4)

Operands

  • Qd
    Destination 128-bit SIMD register
  • Qm
    Key

Reference (Arm A64 ISA)

Instruction Forms

Encoding Instruction ISA Bit pattern
0xCE60C800 SM4EKEY <Vd>.4S, <Vn>.4S, <Vm>.4S A64 11001110011 | Rm | 1 | 1 | 00 | 10 | Rn | Rd
0x4520F000 SM4EKEY <Zd>.S, <Zn>.S, <Zm>.S A64 01000101 | 0 | 0 | 1 | Zm | 11110 | 0 | Zn | Zd

Description

The SM4EKEY instruction reads four rounds of 32-bit input key values from each 128-bit segment of the first source vector, along with four rounds of 32-bit constants from the corresponding 128-bit segment of the second source vector. The four rounds of output key values are derived in accordance with the SM4 standard, and placed in the corresponding segments of the destination vector. This instruction is unpredicated. ID_AA64ZFR0_EL1.SM4 indicates whether this instruction is implemented. This instruction is illegal when executed in Streaming SVE mode, unless FEAT_SME_FA64 is implemented and enabled.

Operation

CheckNonStreamingSVEEnabled();
constant integer VL = CurrentVL;
constant integer segments = VL DIV 128;
bits(VL) operand1 = Z[n, VL];
bits(VL) operand2 = Z[m, VL];
bits(VL) result;

for s = 0 to segments-1
    bits(128) source = Elem[operand2, s, 128];
    bits(32) intval;
    bits(8) sboxout;
    bits(32) const;
    bits(128) roundresult = Elem[operand1, s, 128];

    for index = 0 to 3
        const = Elem[source, 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;

    Elem[result, s, 128] = roundresult;

Z[d, VL] = result;