Получить открытый ключ из сертификата
openssl x509 -inform der -in certificate.der -pubkey -noout > public_key.pem
Creepy Cottonmouth
openssl x509 -inform der -in certificate.der -pubkey -noout > public_key.pem
E:\> openssl x509 -pubkey -noout -in cert.pem > pubkey.pem