In cryptography, PKCS refers to a group of Public Key Cryptography Standards devised and published by RSA Security.
PKCS #7 Cryptographic Message Syntax Standard
PKCS #8 Private-Key Information Syntax Standard.
PKCS #10 Certification Request Standard
PKCS #12 Personal Information Exchange Syntax Standard (PFX文件用的就是这个标准,用来存储私钥)