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KEELOQ Decryption/ Decryption/ /XOR 64 64 XOR

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KEELOQ Decryption/ Decryption/ /XOR 64 64 XOR Cryptanalysis of KeeLoq with COPACOBANA Martin Novotný1,2, Timo Kasper1 1Horst Görtz Institute for IT-Security Ruhr University Bochum 2Faculty of Information Technology Czech Technical University in Prague Case Study Access Control Simple access controls: fixed code (“password”) code eavesdropper duplicates key (cloning) but the industry learned… Case Study Access Control advanced theft control: rolling code code = ek(ni) rolling code (or hopping code) e () is often a code = e (n) k k block cipher code = ek(n+1) code = ek(n+2) …. KeeLoq HoIpNpCRinEMgE CNToSde GeneCOraNtSiToAnNT Synchronization Counter Discrimination Value Func 32 Device 64 KEELOQ Key encryption Derived from Manufacturer Key 32 Hopping Code So what can we do now? If we have access to a remote Recover device key and clone the device People usually do not lend their keys to unknown people In a shop If we have access to a receiver Recover manufacturer key and generate new remotes Identical for all GGaarraaggeeOOppeenneerrss22000000 and corresponding remotes Device Key Derivation Serial Number / SEED 32 32 Manufacturer KEELOQ Key KEELOQ decryption/ decryption/ /XOR 64 64 XOR 32 32 Device Key MS 32 bits Device Key LS 32 bits So what can we do now? After extracting of manufacturing key: Remotely eavesdrop on 1-2 communications & clone key! Serial Number, KeeLoq(n+1) Device Key Derivation 0h SSNe r–ia 1l 2n ubmbSeer r–i a2Sl8 SeN bEruiiaEtmslD nSb u–Eem Er6 bD0/ e Sb–rSiE tE4sE8E DDbi t–s 32 bits scheme #1234 Sniffed from communicatio 32 32 n Manufacturer KEELOQ Key KEELOQ decryption/ decryption/ /XOR 64 64 XOR Retrieve d via 32 DPA 32 Device Key MS 32 bits Device Key LS 32 bits 2P12r68e cccaaonnmddpididuaatedttee vvinaa lulSueeWs 2P3r2e ccaonmpdiduatteed vina lSueWs KeeLoq Cracker KeeLoq Cracker 2 (consecutive) hopping codes sniffe d Hopping Code #1 Hopping Code #2 KEELOQ Device Key KEELOQ decryption Generator decryption Counter1 Discrim1 F1 Counter2 Discrim1 F2 (Counter2 – Counter1) < 7 ? Discrim1F1 == Discrim2F2 ? KEY CANDIDATE Device Key Derivation 0h SSNe r–ia 1l 2n ubmbSeer r–i a2Sl8 SeN bEruiiaEtmslD nSb u–Eem Er6 bD0/ e Sb–rSiE tE4sE8E DDbi t–s 32 bits scheme #1234 32 32 Manufacturer KEELOQ Key KEELOQ decryption/ decryption/ /XOR 64 64 /XOR 32 32 Device Key MS 32 bits Device Key LS 32 bits Precomputed in SW P(r2e1268c coamndpiduattede v ainlu eSsW) PGreecnoempratuetde din i nH SWW KeeLoq Cracker Hopping Code #1 Hopping Code #2 KEELOQ Device Key KEELOQ decryption Generator decryption Counter1 Discrim1 F1 Counter2 Discrim1 F2 (Counter2 – Counter1) < 7 ? Discrim1F1 == Discrim2F2 ? KEY CANDIDATE Device Key Generator Host computer 32 32 bit register 32 bit counter 64 KeeLoq Cracker Hopping Code #1 Hopping Code #2 KEELOQ Device Key KEELOQ decryption Generator decryption Counter1 Discrim1 F1 Counter2 Discrim1 F2 (Counter2 – Counter1) < 7 ? Discrim1F1 == Discrim2F2 ? KEY CANDIDATE KeeLoq – The Algorithm State Registe,ry 7 3 2 42 0 1 1 0 1 0 NLF XOR Key Registe,r k 7 6 5 4 3 2 1 0 0 64 bit key, 32 bit block length NLFSR comprising a 5x1 non-linear function Simple key management: key is constantly rotated 528 rounds, each round one key bit is read Lightweight cipher – cheap and efficient in hardware KeeLoq Encryption • 32 bit block length, 64 bit key • NLFSR comprising a 5x1 non-linear function • Simple key management: key is constantly rotated • 528 rounds, each round one key bit is read Lightweight cipher – cheap and efficient in hardware source: Wikipedia KeeLoq Decryption like encryption, but in reverse order source: Wikipedia KeeLoq Decryption 32 bit state NLF 64 bit key KeeLoq Decryption 32 bit state 64 bit key NLF KeeLoq Decryption 32 bit state 64 bit key NLF KeeLoq Decryption 32 bit state 64 bit key NLF KeeLoq Decryption 32 bit state 64 bit key NLF Unrolled KeeLoq Decryption 32 bit state 64 bit key NLF Unrolled KeeLoq Decryption 32 bit state 64 bit key NLF … … … … Unrolled KeeLoq Decryption 32 bit state 64 bit key NLF … … … … 32 bit state 64 bit key NLF Unrolled KeeLoq Decryption 32 bit state 64 bit key NLF … … … … 32 bit state 64 bit key NLF … … … … Unrolled KeeLoq Decryption 32 bit state 64 bit key NLF … … … … 32 bit state 64 bit key NLF … … … … 32 bit state 64 bit key NLF Unrolled KeeLoq Decryption 32 bit state 64 bit key NLF … … … … 32 bit state 64 bit key NLF … … … … 32 bit state 64 bit key NLF … … … … Unrolled KeeLoq Decryption 32 bit state 64 bit key NLF … … … … 32 bit state 64 bit key NLF 528 x … … … … 32 bit state 64 bit key NLF … … … … Unrolled KeeLoq Decryption 32 bit state 64 bit key NLF … … … … 32 bit state 64 bit key NLF 528 x … … … … th 32 bit state each 464 briot kueny d registered NLF … … … … Unrolled KeeLoq Decryption 32 bit state 64 bit key NLF … … … … 32 bit state 64 bit key NLF … … … … 32 bit state 64 bit key NLF … … … … Unrolled KeeLoq Decryption 32 bit state 64 bit key NLF … … … … 32 bit state 64 bit key NLF … … … … 32 bit state 64 bit key NLF … … … … unrolled decrypter KeeLoq Cracker with 132 pipeline stages Hopping Code #1 Hopping Code #2 KEELOQ Device Key KEELOQ decryption Generator decryption Counter1 Discrim1 F1 Counter2 Discrim1 F2 (Counter2 – Counter1) < 7 ? Discrim1F1 == Discrim2F2 ? KEY CANDIDATE Results fmax = 110 MHz 110 million keys/s verified in 1 FPGA Spartan 3-1000 32 bit seed: 39 seconds / 1 FPGA 48 bit seed: 5.9 hours / 1 COPACOBANA 60 bit seed: 1011 days / 1 COPACOBANA.
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