# Tag Info

## New answers tagged entropy

-1

I want to ask a question: Intel RDRANDOM is only supported by ivy bridge or newer? But my server CPU is old, Can i use it in some method?

3

When you use a PRF to derive a key, there is the potential for collisions. If you derived a 128-bit key from each possible 128-bit number, you'd expect some of them to collide. Specifically, you'd expect only about 63% of all the inputs ($1-e^{-1}$) to appear as outputs. That means you lose less than a bit of entropy even if the original key had the full ...

9

Their numbers are off and the explanation confusing, but they do have a point. The algorithms used for RDRAND/RDSEED instructions are described in the software implementation guide (pdf). What it amounts to is that for RDRAND, some hardware entropy is conditioned and used as a 256-bit seed for AES CTR_DRBG (from SP 800-90A). The same 256-bit seed is used ...

7

It would appear that, in this case, your intuition is correct, and the Intel guy is wrong. When you concatenate two random values, the entropy contained in the concatination depends not only one the entropy of those two sources, but whether they are correlated. If they are entirely uncorrelated, that is, if the probability distribution of one of the random ...

14

Even in context, much of what is written in the blog post makes no sense. E.g., it says: While it can be argued that the DRNG is in reality just splitting a 128-bit value into two pieces and handing them to you one piece at a time, from a theoretical viewpoint this does not matter. While the original value had 128 bits of entropy, the end result is that ...

Top 50 recent answers are included