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+// rng.cpp - written and placed in the public domain by Wei Dai
+
+#include "pch.h"
+#include "rng.h"
+
+#include <time.h>
+#include <math.h>
+
+NAMESPACE_BEGIN(CryptoPP)
+
+// linear congruential generator
+// originally by William S. England
+
+// do not use for cryptographic purposes
+
+/*
+** Original_numbers are the original published m and q in the
+** ACM article above.  John Burton has furnished numbers for
+** a reportedly better generator.  The new numbers are now
+** used in this program by default.
+*/
+
+#ifndef LCRNG_ORIGINAL_NUMBERS
+const word32 LC_RNG::m=2147483647L;
+const word32 LC_RNG::q=44488L;
+
+const word16 LC_RNG::a=(unsigned int)48271L;
+const word16 LC_RNG::r=3399;
+#else
+const word32 LC_RNG::m=2147483647L;
+const word32 LC_RNG::q=127773L;
+
+const word16 LC_RNG::a=16807;
+const word16 LC_RNG::r=2836;
+#endif
+
+byte LC_RNG::GenerateByte()
+{
+	word32 hi = seed/q;
+	word32 lo = seed%q;
+
+	long test = a*lo - r*hi;
+
+	if (test > 0)
+		seed = test;
+	else
+		seed = test+ m;
+
+	return (GETBYTE(seed, 0) ^ GETBYTE(seed, 1) ^ GETBYTE(seed, 2) ^ GETBYTE(seed, 3));
+}
+
+// ********************************************************
+
+X917RNG::X917RNG(BlockTransformation *c, const byte *seed)
+	: cipher(c),
+	  S(cipher->BlockSize()),
+	  dtbuf(S),
+	  randseed(seed, S),
+	  randbuf(S),
+	  randbuf_counter(0)
+{
+	time_t tstamp1 = time(0);
+	xorbuf(dtbuf, (byte *)&tstamp1, STDMIN((int)sizeof(tstamp1), S));
+	cipher->ProcessBlock(dtbuf);
+	clock_t tstamp2 = clock();
+	xorbuf(dtbuf, (byte *)&tstamp2, STDMIN((int)sizeof(tstamp2), S));
+	cipher->ProcessBlock(dtbuf);
+}
+
+byte X917RNG::GenerateByte()
+{
+	if (randbuf_counter==0)
+	{
+		// calculate new enciphered timestamp
+		clock_t tstamp = clock();
+		xorbuf(dtbuf, (byte *)&tstamp, STDMIN((int)sizeof(tstamp), S));
+		cipher->ProcessBlock(dtbuf);
+
+		// combine enciphered timestamp with seed
+		xorbuf(randseed, dtbuf, S);
+
+		// generate a new block of random bytes
+		cipher->ProcessBlock(randseed, randbuf);
+
+		// compute new seed vector
+		for (int i=0; i<S; i++)
+			randseed[i] = randbuf[i] ^ dtbuf[i];
+		cipher->ProcessBlock(randseed);
+
+		randbuf_counter=S;
+	}
+	return(randbuf[--randbuf_counter]);
+}
+
+MaurerRandomnessTest::MaurerRandomnessTest()
+	: sum(0.0), n(0)
+{
+	for (unsigned i=0; i<V; i++)
+		tab[i] = 0;
+}
+
+inline void MaurerRandomnessTest::Put(byte inByte)
+{
+	if (n >= Q)
+		sum += log(double(n - tab[inByte]));
+	tab[inByte] = n;
+	n++;
+}
+
+void MaurerRandomnessTest::Put(const byte *inString, unsigned int length)
+{
+	while (length--)
+		Put(*inString++);
+}
+
+double MaurerRandomnessTest::GetTestValue() const
+{
+	double fTu = (sum/(n-Q))/log(2.0);	// this is the test value defined by Maurer
+
+	double value = fTu * 0.1392;		// arbitrarily normalize it to
+	return value > 1.0 ? 1.0 : value;	// a number between 0 and 1
+}
+
+NAMESPACE_END