From c055f425107cf20c1b8b7c692d5133509dfad52e Mon Sep 17 00:00:00 2001 From: lloyd Date: Tue, 27 Jan 2009 00:16:49 +0000 Subject: Check in a branch with a major redesign on how entropy polling is performed. Combine the fast and slow polls, into a single poll() operation. Instead of being given a buffer to write output into, the EntropySource is passed an Entropy_Accumulator. This handles the RLE encoding that xor_into_buf used to do. It also contains a cached I/O buffer so entropy sources do not individually need to allocate memory for that with each poll. When data is added to the accumulator, the source specifies an estimate of the number of bits of entropy per byte, as a double. This is tracked in the accumulator. Once the estimated entropy hits a target (set by the constructor), the accumulator's member function predicate polling_goal_achieved flips to true. This signals to the PRNG that it can stop performing polling on sources, also polls that take a long time periodically check this flag and return immediately. The Win32 and BeOS entropy sources have been updated, but blindly; testing is needed. The test_es example program has been modified: now it polls twice and outputs the XOR of the two collected results. That helps show if the output is consistent across polls (not a good thing). I have noticed on the Unix entropy source, occasionally there are many 0x00 bytes in the output, which is not optimal. This also needs to be investigated. The RLE is not actually RLE anymore. It works well for non-random inputs (ASCII text, etc), but I noticed that when /dev/random output was fed into it, the output buffer would end up being RR01RR01RR01 where RR is a random byte and 00 is the byte count. The buffer sizing also needs to be examined carefully. It might be useful to choose a prime number for the size to XOR stuff into, to help ensure an even distribution of entropy across the entire buffer space. Or: feed it all into a hash function? This change should (perhaps with further modifications) help WRT the concerns Zack W raised about the RNG on the monotone-dev list. --- checks/common.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'checks') diff --git a/checks/common.h b/checks/common.h index ac3daaf76..fa41882ee 100644 --- a/checks/common.h +++ b/checks/common.h @@ -67,6 +67,8 @@ class Fixed_Output_RNG : public Botan::RandomNumberGenerator return out; } + void reseed(u32bit) {} + void randomize(byte out[], u32bit len) { for(u32bit j = 0; j != len; j++) -- cgit v1.2.3