C.I.E – Carta di Identità Elettronica Functional Specification Version 2.0

• Step 4: APDU command set up in SM_SIG formatThe resulting APDU in SM_SIG format is:CLA INS P1 P2 Lc Data Field LeXCh XX XX XX U+12 P_T_O MAC_OBJ XX11.4.3 APDU in SM_ENC modeWhen an APDU command is transmitted in SM_ENC mode (CLA = XCh) a cipher text iscomputed on the command data field and transmitted in the SM APDU command.• Step 1: set up the Cipher Text Object (C_T_O)Original APDU command structure:CLA INS P1 P2 Lc Data Field LeX0h XX XX XX U Data (U bytes)Computing the Cipher Text:Data FieldData (U bytes)PaddingISO / IEC 9797 method 2 2 (P=1..8 bytes)The Cypher Text Object (C_T_O) is built as follow:T L Value87h U+P+1 Padding Indicator (01h)Cipher Text (U+P bytes)The C_T_O obtained is then composed by W=U+P+3 bytes.• Step 2: APDU command set up in SM_ENC formatCLA INS P1 P2 Lc Data Field LeXCh XX XX XX W C_T_O XX2Padding ISO/IEC 9797 method 2: the data shall be appended with a single ‘80h’ byte. The resulting data shall then beappended with as few (possibly none) ‘00h’ bytes as necessary to obtain a data string whose length (in bytes) is aninteger multiple of 8.CIE - Functional Specification v 2.0 -Page 37/76