void silc_packet_encrypt(SilcCipher cipher, SilcHmac hmac, 
                             SilcBuffer buffer, SilcUInt32 len);

    Encrypts a packet. This also creates HMAC of the packet before 
    encryption and adds the HMAC at the end of the buffer. This assumes
    that there is enough free space at the end of the buffer to add the
    computed HMAC. This is the normal way of encrypting packets, if some
    other process of HMAC computing and encryption is needed this function
    cannot be used.