Section: 10.5.3.2 Authentication Response parameter
Content: The purpose of the authentication response parameter information element is to provide the network with the authentication response calculated in the SIM/USIM. The Authentication Parameter SRES information element is coded as shown in figure 10.5.76/3GPP TS 24.008[ Mobile radio interface Layer 3 specification; Core network protocols; Stage 3 ]  and tables 10.5.90 a & b /3GPP TS 24.008[ Mobile radio interface Layer 3 specification; Core network protocols; Stage 3 ] . The Authentication Response Parameter is a type 3 information element with 5 octets length. In a GSM authentication challenge, the response calculated in the SIM/USIM (SRES) is 4 bytes in length, and is placed in the Authentication Response Parameter information element. In a UMTS authentication challenge, the response calculated in the USIM (RES) may be up to 16 octets in length. The 4 most significant octets shall be included in the Authentication Response Parameter information element. The remaining part of the RES shall be included in the Authentication Response Parameter (extension) IE (see subclause 10.5.3.2.1) Figure 10.5.76/3GPP TS 24.008[ Mobile radio interface Layer 3 specification; Core network protocols; Stage 3 ]  Authentication Response Parameter information element Table 10.5.90a/3GPP TS 24.008[ Mobile radio interface Layer 3 specification; Core network protocols; Stage 3 ] : Authentication Response Parameter information element (SRES) (GSM authentication challenge only) Table 10.5.90b/3GPP TS 24.008[ Mobile radio interface Layer 3 specification; Core network protocols; Stage 3 ] : Authentication Response Parameter information element (RES) (UMTS authentication challenge only)