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/*
*
* Copyright (C) 2021, OFFIS e.V.
* All rights reserved. See COPYRIGHT file for details.
*
* This software and supporting documentation were developed by
*
* OFFIS e.V.
* R&D Division Health
* Escherweg 2
* D-26121 Oldenburg, Germany
*
*
* Module: ofstd
*
* Author: Marco Eichelberg, based on the reference implementation
* of the ISAAC PRNG by Bob Jenkins (Public Domain).
*
* Purpose: Cryptographically secure PRNG based on Bob Jenkins's ISAAC algorithm
*
*/
#include "dcmtk/config/osconfig.h"
#include "dcmtk/ofstd/ofrand.h"
#include "dcmtk/ofstd/ofcast.h"
#include "dcmtk/ofstd/ofstd.h"
#include "dcmtk/ofstd/ofstdinc.h"
#include <ctime>
BEGIN_EXTERN_C
#ifdef HAVE_SYS_TIME_H
#include <sys/time.h>
#endif
END_EXTERN_C
#ifdef HAVE_WINDOWS_H
#define WIN32_LEAN_AND_MEAN
#include <windows.h>
#endif
#define ind(mm,x) ((mm)[(x>>2)&(OFRandom_SIZ-1)])
#define rngstep(mix,a,b,mm,m,m2,r,x) \
{ \
x = *m; \
a = ((a^(mix)) + *(m2++)); \
*(m++) = y = (ind(mm,x) + a + b); \
*(r++) = b = (ind(mm,y>>OFRandom_SIZL) + x) & 0xffffffff; \
}
#define mix(a,b,c,d,e,f,g,h) \
{ \
a^=b<<11; d+=a; b+=c; \
b^=(c&0xffffffff)>>2; e+=b; c+=d; \
c^=d<<8; f+=c; d+=e; \
d^=(e&0xffffffff)>>16; g+=d; e+=f; \
e^=f<<10; h+=e; f+=g; \
f^=(g&0xffffffff)>>4; a+=f; g+=h; \
g^=h<<8; b+=g; h+=a; \
h^=(a&0xffffffff)>>9; c+=h; a+=b; \
}
OFRandom::OFRandom()
: randcnt(OFRandom_SIZ)
, randrsl()
, randmem()
, randa(0)
, randb(0)
, randc(0)
{
/* initialize randrsl based on the current time, CPU clock count, and process ID */
Uint32 tm = OFstatic_cast(Uint32, time(NULL));
Uint32 cl = OFstatic_cast(Uint32, clock());
Uint32 pi = OFstatic_cast(Uint32, OFStandard::getProcessID());
#ifdef _WIN32
ULARGE_INTEGER wintm;
/* tm is number of 100ns ticks since Jan 01 1601.
* We only use the lowest 32 bits of this number.
*/
GetSystemTimeAsFileTime(OFreinterpret_cast(FILETIME *, &wintm));
Uint32 tm2 = OFstatic_cast(Uint32, wintm.LowPart);
#else
struct timeval posixtm;
gettimeofday(&posixtm, NULL);
/* sub-second part of current time in microseconds */
Uint32 tm2 = OFstatic_cast(Uint32, posixtm.tv_usec);
#endif
for (int i=0; i<OFRandom_SIZ; i += 4) // OFRandom_SIZ is dividable by 4
{
randrsl[i] = tm++;
randrsl[i+1] = cl++;
randrsl[i+2] = pi++;
randrsl[i+3] = tm2++;
}
mixSeed();
}
void OFRandom::mixSeed()
{
int i;
Uint32 a,b,c,d,e,f,g,h;
a=b=c=d=e=f=g=h=0x9e3779b9; /* the golden ratio */
for (i=0; i<4; ++i) /* scramble it */
{
mix(a,b,c,d,e,f,g,h);
}
/* initialize using the contents of randrsl[] as the seed */
for (i=0; i<OFRandom_SIZ; i+=8)
{
a+=randrsl[i ]; b+=randrsl[i+1];
c+=randrsl[i+2]; d+=randrsl[i+3];
e+=randrsl[i+4]; f+=randrsl[i+5];
g+=randrsl[i+6]; h+=randrsl[i+7];
mix(a,b,c,d,e,f,g,h);
randmem[i ]=a; randmem[i+1]=b; randmem[i+2]=c; randmem[i+3]=d;
randmem[i+4]=e; randmem[i+5]=f; randmem[i+6]=g; randmem[i+7]=h;
}
/* do a second pass to make all of the seed affect all of m */
for (i=0; i<OFRandom_SIZ; i+=8)
{
a+=randmem[i ]; b+=randmem[i+1];
c+=randmem[i+2]; d+=randmem[i+3];
e+=randmem[i+4]; f+=randmem[i+5];
g+=randmem[i+6]; h+=randmem[i+7];
mix(a,b,c,d,e,f,g,h);
randmem[i ]=a; randmem[i+1]=b; randmem[i+2]=c; randmem[i+3]=d;
randmem[i+4]=e; randmem[i+5]=f; randmem[i+6]=g; randmem[i+7]=h;
}
isaac(); /* fill in the first set of results */}
void OFRandom::seed(Uint32 sval)
{
for (int i=0; i<OFRandom_SIZ; i++)
{
randrsl[i] = sval;
}
randa = 0;
randb = 0;
randc = 0;
mixSeed();
}
void OFRandom::isaac()
{
Uint32 x,y,*m,*m2,*mend;
Uint32 *r = randrsl;
Uint32 a = randa;
Uint32 b = randb + (++randc);
for (m = randmem, mend = m2 = m+(OFRandom_SIZ/2); m<mend; )
{
rngstep( a<<13, a, b, randmem, m, m2, r, x);
rngstep( (a & 0xffffffff) >>6 , a, b, randmem, m, m2, r, x);
rngstep( a<<2 , a, b, randmem, m, m2, r, x);
rngstep( (a & 0xffffffff) >>16, a, b, randmem, m, m2, r, x);
}
for (m2 = randmem; m2<mend; )
{
rngstep( a<<13, a, b, randmem, m, m2, r, x);
rngstep( (a & 0xffffffff) >>6 , a, b, randmem, m, m2, r, x);
rngstep( a<<2 , a, b, randmem, m, m2, r, x);
rngstep( (a & 0xffffffff) >>16, a, b, randmem, m, m2, r, x);
}
randb = b; randa = a;
randcnt = OFRandom_SIZ;
}
Uint32 OFRandom::getRND32()
{
// check if we still have random numbers left
if (randcnt == 0) isaac();
// we use the random numbers from last to first
return randrsl[--randcnt];
}
Uint16 OFRandom::getRND16()
{
// use one 32-bit random number and ignore the extra bits
return OFstatic_cast(Uint16, getRND32());
}
#ifndef OF_NO_UINT64
Uint64 OFRandom::getRND64()
{
// get a 32-bit random number
Uint64 result = getRND32();
// shift into upper 32 bits of the 64-bit word
result <<= 32;
// get a second 32-bit random number
result |= getRND32();
return result;
}
#endif
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