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SM4 encryption and decryption.

The SM4E instruction reads 16 bytes of input data from each 128-bit segment of the first source vector, together with four iterations of 32-bit round keys from the corresponding 128-bit segments of the second source vector. Each block of data is encrypted by four rounds in accordance with the SM4 standard, and destructively placed in the corresponding segments of the first source vector. This instruction is unpredicated.

ID_AA64ZFR0_EL1.SM4 indicates whether this instruction is implemented.


SM4E <Zdn>.S, <Zdn>.S, <Zm>.S

if !HaveSVE2SM4() then UNDEFINED;
integer m = UInt(Zm);
integer dn = UInt(Zdn);

Assembler Symbols


Is the name of the first source and destination scalable vector register, encoded in the "Zdn" field.


Is the name of the second source scalable vector register, encoded in the "Zm" field.


integer segments = VL DIV 128;
bits(VL) operand1 = Z[dn];
bits(VL) operand2 = Z[m];
bits(VL) result;

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

    for index = 0 to 3
        roundkey = Elem[key, index, 32];
        intval = roundresult<127:96> EOR roundresult<95:64> EOR roundresult<63:32> EOR roundkey;

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

        intval = intval EOR ROL(intval, 2) EOR ROL(intval,10) EOR ROL(intval,18) EOR ROL(intval, 24);
        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[dn] = result;

Operational information


  • 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.