smartair/Enhanced Encryptage.md

What is enhanced encryptage?

Enhanced encryptage is a config option that can be turned on in the Smartair software.

The only thing we have observed when turned on is that encoders will "Encrypt" the site ID using the UID as derivation input. However the use of enhanced encryptage is configured by a bit set on the card and not enforced by the reader

We did attempt to encode quite a few credentials using a demo licsense which sets the installation id to AA AA AA AA

Cipher is the value encoded in the SiteId for the given card UID

UID:    FFFFFFFF
Cipher: 9FFFFFFF
 
UID:    00000000
Cipher: AAAAAAAB
 
UID:    00000001
Cipher: 80000001
 
UID:    00000002
Cipher: CB4B4B4A
 
UID:    00000004
Cipher: E5965964
 
UID:    00000008
Cipher: BD198BC3
 
UID:    00000010
Cipher: 21FD2A1E
 
UID:    00000020
Cipher: F9323E49
 
UID:    00000040
Cipher: AE577660
 
UID:    00000080
Cipher: ABFD5109
 
UID:    00000100
Cipher: BB9977DE
 
UID:    00000200
Cipher: AFBD2429
 
UID:    00000400
Cipher: EAA004AA
 
UID:    00000800
Cipher: ABAEDE60
 
UID:    00001000
Cipher: 2AA010EA
 
UID:    00002000
Cipher: AEABDEE5
 
UID:    00004000
Cipher: AA8A0097
 
UID:    00008000
Cipher: AAABFFFC
 
UID:    00010000
Cipher: FAAAF001
 
UID:    00020000
Cipher: BBAAB37E
 
UID:    00040000
Cipher: AEBAA185
 
UID:    00080000
Cipher: ABABAFCE
 
UID:    00100000
Cipher: AAEAB807
 
UID:    00200000
Cipher: EABAA9FE
 
UID:    00400000
Cipher: A2AEAA21
 
UID:    00800000
Cipher: ABABAAFC
 
UID:    01000000
Cipher: AA8AEA81
 
UID:    02000000
Cipher: AAAEBABE
 
UID:    04000000
Cipher: AAAA2EA1
 
UID:    08000000
Cipher: AAAABBAE
 
UID:    10000000
Cipher: AAAAA8E9
 
UID:    20000000
Cipher: AAAAAAFA
 
UID:    40000000
Cipher: AAAAAAA7
 
UID:    AAAAAAAA
Cipher: C6DB6DB6
 
UID:    80000000
Cipher: AAAAAAAA

# Other random tags
UID:    81261454
Cipher: DFB73084

UID:    8B961454
Cipher: 722d963b

UID:    7D861454
Cipher: FF366434

UID:    4426144A
Cipher: B608A00D

UID:    1FD6144B
Cipher: 1C4F6F72

40 (0100)= 10101010 10101010 10101010 10100111 = AA AA AA A7
80 (1000)= 10101010 10101010 10101010 10101010 = AA AA AA AA

The obfuscation is done by a 32‑bit Galois‑style LFSR there is an example set of javascript functions provided.