| 摘要 |
A security circuit for an NMT-mobile radio telephone using SIS (Subscribers Identity Security) comprising a single chip with a CPU and associated memories, wherein the memories storing the authentication key (SAK) for the SIS are divided into accessible areas (202, 206, 208, 222) and nonaccessible areas (220, 204), to which access is allowed only by CPU instructions fetched from a ROM (202) containing internal code enabling reading of the SAK in the secret areas (204), when a call from a subscriber is processed. The new circuit renders it possible to maintain the secrecy of the SAK even though the CPU is connected to external data equipment (130, 140). |
