Worked on the starkware-libs/stwo repository to deliver a targeted fix enhancing cryptographic hashing reliability in Poseidon-based channel operations. Addressed a bug in the Poseidon252Channel by implementing length padding, ensuring the last element of the hash includes the original data length. This adjustment reinforced data integrity and correctness for the Poseidon mix_u32s function, reducing the risk of incorrect hashes in channel computations. The work required a strong understanding of cryptography, hashing algorithms, and low-level programming, and was implemented in Rust. The change improved the security and trustworthiness of the cryptographic primitives used within the library’s core operations.