cryptoProhard

worrier

hxp_39c3

Task: break an SIDH-like isogeny cryptosystem with noisy point pairs to decrypt the flag. Solution: eliminate error terms by multiplying all points by 3^n3 (which kills the error of that order), recover the isogeny via Weil pairing discrete logs on torsion points, then solve for the secret.

$ ls tags/ techniques/
linear_algebraisogenysidhsupersingular_curvesweil_pairingdiscrete_logtorsion_pointsaes_ctrerror_correction
Exploiting error term structure (order dividing 3^n3)Weil pairing for discrete log in torsion subgroupsLinear algebra over Z/2^n2 ZIsogeny recovery from noisy point pairs
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