From PHP function
openssl_public_encrypt ( string $data , string &$crypted , mixed $key )
$key是否只适用于.pem ?或者我们可以用。cer或。crt?
似乎你的标题是错误的，因为openssl_public_encrypt用公钥加密数据，而不是用私钥。但是，这里列出了X.509证书的常见文件名扩展名:
.pem (Privacy Enhanced Mail) Base64 encoded DER certificate
enclosed between "-----BEGIN CERTIFICATE-----" and
"-----END CERTIFICATE-----"
.cer, .crt, .der usually in binary DER form, but Base64-encoded certificates are
common too (see .pem above)
.p7b, .p7c PKCS#7 SignedData structure without data, just certificate(s)
or CRL(s)
.p12 PKCS#12, may contain certificate(s) (public) and private keys
(password protected)
.pfx PFX, predecessor of PKCS#12 (usually contains data in PKCS#12
format, e.g., with PFX files generated in IIS)