67 lines
1.5 KiB
Plaintext
67 lines
1.5 KiB
Plaintext
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# Amended Needham Schroeder Symmetric Key
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#
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# Modelled after the description in the SPORE library
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# http://www.lsv.ens-cachan.fr/spore/nssk_amended.html
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#
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#
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# Note:
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# According to SPORE there are no attacks on this protocol, scyther
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# finds one however. This has to be investigated further.
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# Model dec that is invertible by inc
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const dec,inc: Function;
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inversekeys(dec,inc);
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usertype SessionKey;
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const Fresh: Function;
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const Compromised: Function;
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protocol needhamschroedersk-amend(I,R,S)
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{
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role I
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{
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fresh Ni: Nonce;
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var Nr: Nonce;
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var Kir: SessionKey;
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var T,T2: Ticket;
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send_1(I,R,I);
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read_2(R,I,T);
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send_3(I,S,(I,R,Ni,T));
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read_4(S,I, {Ni,R,Kir,T2}k(I,S));
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send_5(I,R,T2);
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read_6(R,I,{Nr}Kir);
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send_7(I,R,{{Nr}dec}Kir);
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claim_I2(I,Secret,Kir);
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claim_I3(I,Nisynch);
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claim_I4(I,Empty,(Fresh,Kir));
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}
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role R
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{
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fresh Nr: Nonce;
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var Kir: SessionKey;
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read_1(I,R,I);
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send_2(R,I,{I,Nr}k(R,S));
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read_5(I,R,{Kir,Nr,I}k(R,S));
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send_6(R,I,{Nr}Kir);
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read_7(I,R,{{Nr}dec}Kir);
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claim_R1(R,Secret,Nr);
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claim_R3(R,Nisynch);
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claim_R4(R,Empty,(Fresh,Kir));
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}
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role S
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{
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var Ni,Nr: Nonce;
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fresh Kir: SessionKey;
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read_3(I,S,(I,R,Ni,{I,Nr}k(R,S)));
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send_4(S,I,{Ni,R,Kir,{Kir,Nr,I}k(R,S)}k(I,S));
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}
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}
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