Lattices
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Posts
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Small ROS: Eighty-One Random-Oracle Equations That Collapse Into One Subset-Sum
A write-up of the crypto challenge Small ROS from the m0leCon 2026 finals, where choosing the rows of an overdetermined random-oracle system turns eighty of its equations into coordinate lookups, leaves one, and reduces the whole verifier to a modular subset-sum that a lattice solves.
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CO: A Cubic Surface, a Hyperplane Section, and a Flag Collected One Small Prime at a Time
A write-up of the crypto challenge CO from WannaGame Championship 2025, where the group lives on a cubic surface in projective 3-space, a hyperplane through the given points cuts it into an ordinary elliptic curve, and the same secret scalar reused across attacker-chosen primes falls to Pohlig-Hellman and the CRT.
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Interesting Signing: One Byte Into the Modulus, Then an Orthogonal Lattice Factors It
A write-up of the crypto challenge Interesting Signing from WannaGame Championship 2025, where a one-byte overflow into the RSA modulus turns the CRT recombination into a linear equation over the integers, and ten of those equations let an orthogonal lattice recover the private CRT coefficients and factor a 3072-bit modulus.
