1 files changed, 63 insertions, 0 deletions
diff --git a/CryptoPP/blumshub.cpp b/CryptoPP/blumshub.cpp
new file mode 100644
index 000000000..be9b75829
--- /dev/null
+++ b/CryptoPP/blumshub.cpp
@@ -0,0 +1,63 @@
+// blumshub.cpp - written and placed in the public domain by Wei Dai
+
+#include "pch.h"
+#include "blumshub.h"
+
+NAMESPACE_BEGIN(CryptoPP)
+
+PublicBlumBlumShub::PublicBlumBlumShub(const Integer &n, const Integer &seed)
+	: modn(n),
+	  maxBits(BitPrecision(n.BitCount())-1)
+{
+	current = modn.Square(modn.Square(seed));
+	bitsLeft = maxBits;
+}
+
+unsigned int PublicBlumBlumShub::GenerateBit()
+{
+	if (bitsLeft==0)
+	{
+		current = modn.Square(current);
+		bitsLeft = maxBits;
+	}
+
+	return current.GetBit(--bitsLeft);
+}
+
+byte PublicBlumBlumShub::GenerateByte()
+{
+	byte b=0;
+	for (int i=0; i<8; i++)
+		b = (b << 1) | PublicBlumBlumShub::GenerateBit();
+	return b;
+}
+
+void PublicBlumBlumShub::GenerateBlock(byte *output, size_t size)
+{
+	while (size--)
+		*output++ = PublicBlumBlumShub::GenerateByte();
+}
+
+void PublicBlumBlumShub::ProcessData(byte *outString, const byte *inString, size_t length)
+{
+	while (length--)
+		*outString++ = *inString++ ^ PublicBlumBlumShub::GenerateByte();
+}
+
+BlumBlumShub::BlumBlumShub(const Integer &p, const Integer &q, const Integer &seed)
+	: PublicBlumBlumShub(p*q, seed),
+	  p(p), q(q),
+	  x0(modn.Square(seed))
+{
+}
+
+void BlumBlumShub::Seek(lword index)
+{
+	Integer i(Integer::POSITIVE, index);
+	i *= 8;
+	Integer e = a_exp_b_mod_c (2, i / maxBits + 1, (p-1)*(q-1));
+	current = modn.Exponentiate(x0, e);
+	bitsLeft = maxBits - i % maxBits;
+}
+
+NAMESPACE_END