Implmented Bernstein\'s Tweaked Roots for Rabin-Williams signatures. Thanks to Evgeny Sidorov for suggesting it

git-svn-id: svn://svn.code.sf.net/p/cryptopp/code/trunk/c5@565 57ff6487-cd31-0410-9ec3-f628ee90f5f0

1 files changed, 16 insertions, 2 deletions

diff --git a/rw.h b/rw.h
index 6820251..45b3946 100644
--- a/rw.h
+++ b/rw.h
@@ -48,8 +48,9 @@ class CRYPTOPP_DLL InvertibleRWFunction : public RWFunction, public TrapdoorFunc
 	typedef InvertibleRWFunction ThisClass;
 
 public:
-	void Initialize(const Integer &n, const Integer &p, const Integer &q, const Integer &u)
-		{m_n = n; m_p = p; m_q = q; m_u = u;}
+	InvertibleRWFunction() : m_precompute(false) {}
+
+	void Initialize(const Integer &n, const Integer &p, const Integer &q, const Integer &u);
 	// generate a random private key
 	void Initialize(RandomNumberGenerator &rng, unsigned int modulusBits)
 		{GenerateRandomWithKeySize(rng, modulusBits);}
@@ -79,8 +80,21 @@ public:
 	void SetPrime2(const Integer &q) {m_q = q;}
 	void SetMultiplicativeInverseOfPrime2ModPrime1(const Integer &u) {m_u = u;}
 
+	virtual bool SupportsPrecomputation() const {return true;}
+	virtual void Precompute(unsigned int unused = 0) {PrecomputeTweakedRoots();}
+	virtual void Precompute(unsigned int unused = 0) const {PrecomputeTweakedRoots();}
+
+	virtual void LoadPrecomputation(BufferedTransformation &storedPrecomputation);
+	virtual void SavePrecomputation(BufferedTransformation &storedPrecomputation) const;
+
+protected:
+	void PrecomputeTweakedRoots() const;
+
 protected:
 	Integer m_p, m_q, m_u;
+
+	mutable Integer m_pre_2_9p, m_pre_2_3q, m_pre_q_p;
+	mutable bool m_precompute;
 };
 
 //! RW