Update comments

1 files changed, 13 insertions, 12 deletions

diff --git a/elgamal.h b/elgamal.h
index dac84f32..1c5fcb22 100644
--- a/elgamal.h
+++ b/elgamal.h
@@ -203,24 +203,24 @@ struct DL_PrivateKey_ElGamal : public BASE
 	/// \details Level 0 does not require a RandomNumberGenerator. A NullRNG() can

 	///  be used for level 0. Level 1 may not check for weak keys and such.

 	///  Levels 2 and 3 are recommended.

-	bool Validate(RandomNumberGenerator &rng, unsigned int level) const

+	virtual bool Validate(RandomNumberGenerator &rng, unsigned int level) const

 	{

 		// Validate() formerly used DL_PrivateKey_GFP implementation through

 		// inheritance. However, it would reject keys from other libraries

-		// like BouncyCastle. The failure was x < q. To avoid the failure

-		// Crypto++ would perform a reduction on x when loaded using

-		// DL_PublicKey_GFP_OldFormat. Also see

+		// like BouncyCastle. The failure was x < q. According to ElGamal's

+		// paper and the HAC, the private key is selected in over [1,p-1],

+		// Later Tsiounis and Yung showed the lower limit as [1,q-1] in

+		// "On the Security of EIGamal Based Encryption". As such, Crypto++

+		// will generate a key in the range [1,q-1], but accept a key

+		// in [1,p-1]. Thanks to JPM for finding the reference. Also see

 		// https://github.com/weidai11/cryptopp/commit/a5a684d92986.

-		// According to ElGamal's paper and the HAC, the private key is

-		// selected in over [1,p-1], and not [1,q-1] as with some of the

-		// later GFP algorithms.

 

-		CRYPTOPP_ASSERT(this->GetAbstractGroupParameters().Validate(rng, level));

-		bool pass = this->GetAbstractGroupParameters().Validate(rng, level);

+		CRYPTOPP_ASSERT(GetAbstractGroupParameters().Validate(rng, level));

+		bool pass = GetAbstractGroupParameters().Validate(rng, level);

 

-		const Integer &p = this->GetGroupParameters().GetModulus();

-		const Integer &q = this->GetAbstractGroupParameters().GetSubgroupOrder();

-		const Integer &x = this->GetPrivateExponent();

+		const Integer &p = GetGroupParameters().GetModulus();

+		const Integer &q = GetAbstractGroupParameters().GetSubgroupOrder();

+		const Integer &x = GetPrivateExponent();

 

 		// Changed to x < p-1 based on ElGamal's paper and the HAC.

 		CRYPTOPP_ASSERT(x.IsPositive());

@@ -229,6 +229,7 @@ struct DL_PrivateKey_ElGamal : public BASE
 

 		if (level >= 1)

 		{

+			// Minimum security level due to Tsiounis and Yung.

 			CRYPTOPP_ASSERT(Integer::Gcd(x, q) == Integer::One());

 			pass = pass && Integer::Gcd(x, q) == Integer::One();

 		}