The invention relates to method and system for using PKCS and especially PKCS#10 registration standard on a mobile environment and in particularly in a WPKI (Wireless PKI) environment comprising a registration server and a client provided with a key pair is provided only with a part of the certificate request info defined on the PKCS registration standard. A PKCS registration structure is formed by the client of said part of the certificate request info and the public key to be registered, after which a verifying code is determined using at least part of said formed PKCS registration structure. Finally said verifying code and the public key are delivered to the registration server advantageously without delivering said part of the certificate request info received at first by the client.