Here we introduce an improved approach to Variational Quantum Attack
Algorithms (VQAA) on crytographic protocols. Our methods provide robust quantum
attacks to well-known cryptographic algorithms, more efficiently and with
remarkably fewer qubits than previous approaches. We implement simulations of
our attacks for symmetric-key protocols such as S-DES, S-AES and Blowfish. For
instance, we show how our attack allows a classical simulation of a small
8-qubit quantum computer to find the secret key of one 32-bit Blowfish instance
with 24 times fewer number of iterations than a brute-force attack. Our work
also shows improvements in attack success rates for lightweight ciphers such as
S-DES and S-AES. Further applications beyond symmetric-key cryptography are
also discussed, including asymmetric-key protocols and hash functions. In
addition, we also comment on potential future improvements of our methods. Our
results bring one step closer assessing the vulnerability of large-size
classical cryptographic protocols with Noisy Intermediate-Scale Quantum (NISQ)
devices, and set the stage for future research in quantum cybersecurity.

改进的变分量子攻击算法 (VQAA) 提供了针对众所周知的加密算法的强大的量子攻击方法，效率更高，所需量子位数明显较少。我们对对称密钥协议（如 S-DES，S-AES 和 Blowfish）的攻击进行了模拟，结果表明我们的攻击允许一个小型 8 量子比特量子计算机在 24 次迭代次数更少的情况下，通过经典模拟找到一个 32 比特 Blowfish 实例的秘密密钥。我们的工作还展示了轻量级密码（如 S-DES 和 S-AES）的攻击成功率的改进。此外，我们还讨论了超过对称密钥密码学的应用，包括非对称密钥协议和哈希函数。我们的结果使得使用嘈杂中间规模量子（NISQ）设备评估大型经典加密协议的易受攻击性更加接近，并为量子网络安全性的未来研究奠定了基础。