Section: C.3 Elliptic Curve Integrated Encryption Scheme (ECIES) C.3.1 General
Content: The use of ECIES for concealment of the SUPI shall adhere to the SECG specifications [29] and [30]. Processing on UE side and home network side are described in high level in clauses C.3.2 and C.3.3. When the SUPI is of type IMSI, the subscription identifier part of the IMSI (i.e., MSIN) that is used to construct the scheme-input shall be coded as hexadecimal digits using packed BCD coding where the order of digits within an octet is same as the order of MSIN digits specified in Figure 9.11.3.4.3a of TS 24.501[ Non-Access-Stratum (NAS) protocol for 5G System (5GS); Stage 3 ]  [35]. If the MSIN is composed of an odd number of digits, then the bits 5 to 8 of final octet shall be coded as "1111". When the SUPI is of type network specific identifier, the subscription identifier part of the SUPI that is used to construct the scheme-input shall follow the encoding rules specified in Annex B.2.1.2 of TS 33.220[ Generic Authentication Architecture (GAA); Generic Bootstrapping Architecture (GBA) ]  [28].