/dev/random权限被拒绝

6
我正在阅读关于随机数及其生成的内容。自从我开始编程以来,我就对随机性产生了兴趣。我读到Linux内核也使用随机数生成体系结构。
The structure consists of a two-level cascaded sequence of pools coupled with 
CSPRNGs.
Each pool is a large group of bits which represents the current state of the 
random number generator. The CSPRNGs are currently based on SHA-1, but the 
kernel developers are considering a switch to SHA-3.

The kernel RNG produces two user-space output streams. One of these goes to 
/dev/urandom and also to the kernel itself; the latter is useful because there 
are uses for random numbers within the kernel. The other output stream goes to
/dev/random. The difference between the two is that /dev/random tries to estimate
how much entropy is coming into the system, and will throttle its output if there 
is insufficient entropy. By contrast, the /dev/urandom stream does not throttle
output, and if users consume all of the available entropy, the interface degrades
to a pure CSPRNG.

因此,我充满激情地尝试进入并检查/dev/random和/dev/urandom中的内容。但它说:

root@ubuntu:/home/sunny# /dev/random
bash: /dev/random: Permission denied

root@ubuntu:/home/sunny# /dev/urandom
bash: /dev/urandom: Permission denied

然而,当我使用“ls”命令检查时,我可以在/dev中看到“random”。我想详细了解这个。

1个回答

16

/dev/random不是可执行文件。尝试使用cat /dev/random命令。或者,如果你不想测试你的反应速度,dd if=/dev/random bs=128 count=1命令会显示有限数量的随机字符。


8
尽管要准备快速按下Ctrl-c... - Xymostech
1
@Xymostech 是的,但如果您能够重新获得终端,您肯定会看到“里面有什么”。 - ldav1s
2
是的,@Xymostech,我已经准备好了。谢谢。是我强制它生成随机数吗?还是它只是显示那些已经存储在其中的随机内容? - Sunny
2
考虑使用hexdump而不是cat... - Chris Stratton
十六进制转储示例:$ > head /dev/urandom | hexdump - Fábio Almeida

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