This is supported on
target_arch="riscv64"
only.Expand description
P1
transformation function as is used in the SM3 hash algorithm
This function is included in Zksh
extension. It’s defined as:
P1(X) = X ⊕ (X ≪ 15) ⊕ (X ≪ 23)
where ⊕
represents 32-bit xor, and ≪ k
represents rotate left by k
bits.
In the SM3 algorithm, the P1
transformation is used to expand message,
where expanded word Wj
can be generated from the previous words.
The whole process can be described as the following pseudocode:
FOR j=16 TO 67
Wj ← P1(Wj−16 ⊕ Wj−9 ⊕ (Wj−3 ≪ 15)) ⊕ (Wj−13 ≪ 7) ⊕ Wj−6
ENDFOR
According to RISC-V Cryptography Extensions, Volume I, the execution latency of this instruction must always be independent from the data it operates on.