How Does the Use of RIPEMD-160 Reduce the Risk of Quantum Computing Attacks?

The use of RIPEMD-160, a 160-bit hash function, does not inherently reduce the risk of quantum computing attacks compared to SHA-256. Quantum computers, utilizing Grover's algorithm, could potentially speed up preimage attacks on an N-bit hash from O(2^N) to O(2^(N/2)).

Therefore, a 160-bit hash is less secure than a 256-bit hash against a quantum preimage attack. The main protection is the exposure model (key is only revealed upon spending).