VIA PadLock is a central processing unit (CPU) instruction set extension to the x86 microprocessor instruction set architecture (ISA) found on processors produced by VIA Technologies and Zhaoxin.
Introduced in 2003 with the VIA Centaur CPUs, the additional instructions provide hardware-accelerated random number generation (RNG), Advanced Encryption Standard (AES), SHA-1, SHA256, and Montgomery modular multiplication.
If the resultant EAX >= 0xC0000001, the CPU is aware of Centaur features.
An additional request with EAX = 0xC0000001 then returns PadLock support in EDX.
[1] VIA PadLock found on some Zhaoxin CPUs have SM3 hashing and SM4 block cipher added.