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https://issues.apache.org/jira/browse/HADOOP-10734?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14051427#comment-14051427
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Yi Liu commented on HADOOP-10734:
---------------------------------
Thanks [~cmccabe], [~apurtell], [~andrew.wang] for the comments.
I summarize several ways to generate secure random in linux, and why RdRand.
* /dev/random, it uses an entropy pool of several entropy sources, such as
mouse movement, keyboard type and so on. If entropy pool is empty, reads to
/dev/random will be blocked until additional environment noise is gathered.
RdRand is used to improve the entropy by combining the values received from
RdRand with other sources of randomness.
The reason of the combining way is some developers concern there may be
back doors in RdRand, but it’s not true.
* /dev/urandom, it reuses the internal entropy pool and will return as many
random bytes as requested. The call will not block, and the outpout may contain
less entropy than the corresponding read from /dev/random. If the entropy pool
is empty, it will generate data using SHA or other algorithms.
* In java, new SecureRandom(), will read bytes from /dev/urandom and do {{xor}}
with bytes from java SHA1PRNG.
* RdRand, hardware generator. In Openssl, it’s recommended to use hardware
generators, it says their entropy is always nearly 100%. We can use RdRand
directly.
So we can see, option 4, the RdRand is faster than others and the entropy is
nearly 100%.
http://en.wikipedia.org/wiki/RdRand
http://wiki.openssl.org/index.php/Random_Numbers
http://en.wikipedia.org/?title=/dev/random
http://docs.oracle.com/javase/7/docs/api/java/security/SecureRandom.html
> Implementation of true secure random with high performance using hardware
> random number generator.
> --------------------------------------------------------------------------------------------------
>
> Key: HADOOP-10734
> URL: https://issues.apache.org/jira/browse/HADOOP-10734
> Project: Hadoop Common
> Issue Type: Sub-task
> Components: security
> Affects Versions: fs-encryption (HADOOP-10150 and HDFS-6134)
> Reporter: Yi Liu
> Assignee: Yi Liu
> Fix For: fs-encryption (HADOOP-10150 and HDFS-6134)
>
> Attachments: HADOOP-10734.patch
>
>
> This JIRA is to implement Secure random using JNI to OpenSSL, and
> implementation should be thread-safe.
> Utilize RdRand to return random numbers from hardware random number
> generator. It's TRNG(True Random Number generators) having much higher
> performance than {{java.security.SecureRandom}}.
> https://wiki.openssl.org/index.php/Random_Numbers
> http://en.wikipedia.org/wiki/RdRand
> https://software.intel.com/en-us/articles/performance-impact-of-intel-secure-key-on-openssl
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