We propose a new quantum-assisted digital signature (Q-DS) protocol based on the composite of truly random symmetric keys generated by quantum key distribution with secure standardized hash functions, which allows for high parameterization to provide different security levels. The protocol is demonstrated to be secure, it is implemented, and its performance is tested for several system configurations. A comparative evaluation of the results obtained for Q-DS is carried out with 6 pre-quantum and 12 post-quantum digital signature algorithms. The results show that the Q-DS overperforms during the signature generation and verification processes, while its performance is affected by the key generation process. However, using more efficient QKD devices, this process can be highly improved, making the Q-DS protocol comparable to the most efficient post-quantum solution, i.e., CRYSTALS-Dilithium.