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SM4 Encode takes input data as a 128-bit vector from the first source SIMD&FP register, and four iterations of the round key held as the elements of the 128-bit vector in the second source SIMD&FP register. It encrypts the data by four rounds, in accordance with the SM4 standard, returning the 128-bit result to the destination SIMD&FP register.

This instruction is implemented only when ARMv8.2-SM is implemented.

Advanced SIMD


Advanced SIMD

SM4E <Vd>.4S, <Vn>.4S

if !HaveSM4Ext() then UNDEFINED;
integer d = UInt(Rd);
integer n = UInt(Rn);

Assembler Symbols


Is the name of the SIMD&FP source and destination register, encoded in the "Rd" field.


Is the name of the second SIMD&FP source register, encoded in the "Rn" field.



bits(128) Vn = V[n];
bits(32) intval; 
bits(8) sboxout;
bits(128) roundresult;
bits(32) roundkey;

for index = 0 to 3
    roundkey = Elem[Vn,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; 
V[d] = roundresult;

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.