为什么 /dev/urandom 不阻塞？
Why does /dev/urandom not block?
我知道/dev/random阻塞等待更多的熵进来，但为什么/dev/urandom不阻塞？
因为它的目的不是阻塞。这就是它与 /dev/random 的真正区别。所以你不必担心阻塞，但是你从中得到的位可能不像从 /dev/random.
中得到的那样随机。
根据man page：
If there is not sufficient entropy in the entropy pool, the returned
values from /dev/urandom are theoretically vulnerable to a
cryptographic attack on the algorithms used by the driver.
手册页添加：
Knowledge of how to do this is not available in the current
unclassified literature, but it is theoretically possible that such an
attack may exist.
我知道/dev/random阻塞等待更多的熵进来，但为什么/dev/urandom不阻塞？
因为它的目的不是阻塞。这就是它与 /dev/random 的真正区别。所以你不必担心阻塞，但是你从中得到的位可能不像从 /dev/random.
根据man page：
If there is not sufficient entropy in the entropy pool, the returned values from
/dev/urandomare theoretically vulnerable to a cryptographic attack on the algorithms used by the driver.
手册页添加：
Knowledge of how to do this is not available in the current unclassified literature, but it is theoretically possible that such an attack may exist.