src/random.h

   1 // Copyright (c) 2009-2010 Satoshi Nakamoto
   2 // Copyright (c) 2009-2016 The Bitcoin Core developers
   3 // Distributed under the MIT software license, see the accompanying
   4 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
   5
   6 #ifndef BITCOIN_RANDOM_H
   7 #define BITCOIN_RANDOM_H
   8
   9 #include "uint256.h"
  10
  11 #include <stdint.h>
  12
  13 /* Seed OpenSSL PRNG with additional entropy data */
  14 void RandAddSeed();
  15
  16 /**
  17  * Functions to gather random data via the OpenSSL PRNG
  18  */
  19 void GetRandBytes(unsigned char* buf, int num);
  20 uint64_t GetRand(uint64_t nMax);
  21 int GetRandInt(int nMax);
  22 uint256 GetRandHash();
  23
  24 /**
  25  * Function to gather random data from multiple sources, failing whenever any
  26  * of those source fail to provide a result.
  27  */
  28 void GetStrongRandBytes(unsigned char* buf, int num);
  29
  30 /**
  31  * Fast randomness source. This is seeded once with secure random data, but
  32  * is completely deterministic and insecure after that.
  33  * This class is not thread-safe.
  34  */
  35 class FastRandomContext {
  36 public:
  37     explicit FastRandomContext(bool fDeterministic=false);
  38
  39     uint32_t rand32() {
  40         Rz = 36969 * (Rz & 65535) + (Rz >> 16);
  41         Rw = 18000 * (Rw & 65535) + (Rw >> 16);
  42         return (Rw << 16) + Rz;
  43     }
  44
  45     uint32_t Rz;
  46     uint32_t Rw;
  47 };
  48
  49 /* Number of random bytes returned by GetOSRand.
  50  * When changing this constant make sure to change all call sites, and make
  51  * sure that the underlying OS APIs for all platforms support the number.
  52  * (many cap out at 256 bytes).
  53  */
  54 static const ssize_t NUM_OS_RANDOM_BYTES = 32;
  55
  56 /** Get 32 bytes of system entropy. Do not use this in application code: use
  57  * GetStrongRandBytes instead.
  58  */
  59 void GetOSRand(unsigned char *ent32);
  60
  61 /** Check that OS randomness is available and returning the requested number
  62  * of bytes.
  63  */
  64 bool Random_SanityCheck();
  65
  66 #endif // BITCOIN_RANDOM_H