Compute the KDC-REP length
KDC-REP : 0x30 L1 KDC-REP sequence | +--> 0xA0 0x03 pvno tag | | | +--> 0x02 0x01 0x05 pvno (5) | +--> 0xA1 0x03 msg-type tag | | | +--> 0x02 0x01 0x0B/0x0D msg-type : either AS-REP (0x0B) or TGS-REP (0x0D) | +--> 0xA2 L2 pa-data tag | | | +--> 0x30 L2-1 pa-data SEQ | | | +--> 0x30 L2-1-1 pa-data | | | +--> 0x30 L2-1-2 pa-data | : | +--> 0xA3 L3 crealm tag | | | +--> 0x1B L3-1 crealm | +--> 0xA4 L4 cname tag | | | +--> 0x30 L4-1 cname | +--> 0xA5 L5 ticket tag | | | +--> 0x61 L5-1 ticket | +--> 0xA6 L6 enc-part tag | +--> 0x30 L6-1 enc-part