8 partial deconstructions when I try to implement a timeout rule.

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A. Y.

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May 22, 2026, 7:20:10 AMMay 22
to Tamarin-prover
Hi, I'm working on a challenge-response protocol that can detect prover response losses. The idea was for the prover itself to be the observer of the detection, receiving a challenge where the verifier's state doesn't match the prover's updated state.
However, to implement response loss detection, I need to include a challenge timeout rule. This prevents deadlocks due to the fact that the verifier is stateful and, once it sends a challenge, would remain in the verify state forever if we don't implement the timeout.
However, as soon as I insert the timeout rule, the GUI displays eight partial constructions, causing almost all my lemmas to fail.

rule Register:
    [ ... ]
  --[ ... ]-->
    [ ...
      St_V_Challenge(~idV, %1, 'null'),
      ... ]
rule V_challenge:
    [ ...
      St_V_Challenge(~idV, %prev_cP, prev_nP),
      Fr(~ch),
      ... ]
  --[ ... ]-->
    [ ...
      St_V_Verify(~idV, %prev_cP, prev_nP, ~ch),
      ... ]
rule V_timeout:
    [ ...
      St_V_Verify(~idV, %prev_cP, prev_nP, ~ch),
      ... ]
  --[ ... ]-->
    [ ...
      St_V_Challenge(~idV, %prev_cP, prev_nP),
      ... ]

Nikodem Witkiewicz

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May 25, 2026, 10:10:39 AMMay 25
to tamarin...@googlegroups.com
Hi,
There are a few options for solving partial deconstructions.
You may:
  • use the --auto-sources flag;
  • resolve them yourself by writing source lemmas;
  • use some modelling tricks (check out the manual).
I highly recommend reading Tamarin book and the manual. 

Cheers,
Nikodem

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