Challenge Cipher

tos.img keybox
tsec wrapper reads aid


Challenge Flow:

1. Client sends UID to Server (device android_id; "e816ebb8-44b7-3a37-9398-47ec566a63cd")
2. Server responds with Challenge (always identical ; "NVSI_2.00") and R1 (random)
3. Client sends UID again, (Google) Keybox ID, AID (all consistent on the same device) and R1 Solved to Server
4. Server verifies R1 Solved

5. More follows e.g. server responds with a 16 byte session ID and the client sends a further encrypted version back alongside a new random value (always random even if the server presents the same R1 every time, indicating seed and/or nonce in RandState is client randomized)

Map of struct storing all the variables related to randomization Client can access (48 bytes):

struct RandState {
u8 seed[16];
u32_t ctr; //maybe indicates CTR mode e.g.the use of a stream cipher?
u8 pad[12];
u32 nonce[2];
u8 pad2[8];
}

//this might not get used during the Challenge Flow but later on during the Session Flow


Consistent Values:

AID:
1C1DFE67

UID:
B8EB16E8 B744373A 98936A56 EC47CD63 (0xB8EB16E8B744373A98936A56EC47CD63)

Keybox ID:
6235D3E3 30DEC513 4DC9DABB 59FF02F6 (0x6235D3E330DEC5134DC9DABB59FF02F6)

Challenge:
2E2E2E2E 4E565349 5F322E30 2E2E2E2E (0x2E2E2E2E4E5653495F322E302E2E2E2E)

Random Values:

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R1:
64446751 086DC976 F1743D0A 948BB1C7 (0x64446751086DC976F1743D0A948BB1C7)

R1 Solved:
279F9999 AA8A9BB3 F0CEAD54 0031CC42 (0x279F9999AA8A9BB3F0CEAD540031CC42)
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R1:
413B94DF B8BBD22B 1C770906 F59AD00B (0x413B94DFB8BBD22B1C770906F59AD00B)

R1 Solved:
10817F2D 79A056D5 CC68FCED 96077B17 (0x10817F2D79A056D5CC68FCED96077B17)
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