Add SecretToPublicKey function for x25519

1 files changed, 19 insertions, 11 deletions

diff --git a/xed25519.cpp b/xed25519.cpp
index 6cc8ecb0..6207e7e1 100644
--- a/xed25519.cpp
+++ b/xed25519.cpp
@@ -116,8 +116,8 @@ x25519::x25519(const Integer &x)
 x25519::x25519(RandomNumberGenerator &rng)

 {

     rng.GenerateBlock(m_sk, SECRET_KEYLENGTH);

-    m_sk[0] &= 248; m_sk[31] &= 127; m_sk[31] |= 64;

-    Donna::curve25519_mult(m_pk, m_sk);

+    ClampKey(m_sk);

+    SecretToPublicKey(m_pk, m_sk);

 }

 

 x25519::x25519(BufferedTransformation &params)

@@ -125,10 +125,9 @@ x25519::x25519(BufferedTransformation &params)
     Load(params);

 }

 

-void x25519::ClampKeys(byte y[PUBLIC_KEYLENGTH], byte x[SECRET_KEYLENGTH]) const

+void x25519::ClampKey(byte x[SECRET_KEYLENGTH]) const

 {

     x[0] &= 248; x[31] &= 127; x[31] |= 64;

-    Donna::curve25519_mult(y, x);

 }

 

 bool x25519::IsClamped(const byte x[SECRET_KEYLENGTH]) const

@@ -141,6 +140,11 @@ bool x25519::IsSmallOrder(const byte y[PUBLIC_KEYLENGTH]) const
     return HasSmallOrder(y);

 }

 

+void x25519::SecretToPublicKey(byte y[PUBLIC_KEYLENGTH], const byte x[SECRET_KEYLENGTH]) const

+{

+    Donna::curve25519_mult(y, x);

+}

+

 void x25519::BERDecodeAndCheckAlgorithmID(BufferedTransformation &bt)

 {

     // We have not yet determined the OID to use for this object.

@@ -269,10 +273,10 @@ bool x25519::Validate(RandomNumberGenerator &rng, unsigned int level) const
         return false;

     if (level >= 3)

     {

-        SecByteBlock sk(m_sk, SECRET_KEYLENGTH), pk(PUBLIC_KEYLENGTH);

-        ClampKeys(pk, sk);

+        // Verify m_pk is pairwise consistent with m_sk

+        SecByteBlock pk(PUBLIC_KEYLENGTH);

+        SecretToPublicKey(pk, m_sk);

 

-        // Secret key is already clamped, bufs are equal

         if (VerifyBufsEqual(pk, m_pk, PUBLIC_KEYLENGTH) == false)

             return false;

     }

@@ -327,6 +331,10 @@ void x25519::AssignFrom(const NameValuePairs &source)
     {

         m_oid = oid;

     }

+

+    bool derive = false;

+    if (source.GetValue("DerivePublicKey", derive) && derive == true)

+        SecretToPublicKey(m_pk, m_sk);

 }

 

 void x25519::GenerateRandom(RandomNumberGenerator &rng, const NameValuePairs &params)

@@ -336,20 +344,20 @@ void x25519::GenerateRandom(RandomNumberGenerator &rng, const NameValuePairs &pa
         rng.IncorporateEntropy(seed.begin(), seed.size());

 

     rng.GenerateBlock(m_sk, SECRET_KEYLENGTH);

-    m_sk[0] &= 248; m_sk[31] &= 127; m_sk[31] |= 64;

-    Donna::curve25519_mult(m_pk, m_sk);

+    ClampKey(m_sk);

+    SecretToPublicKey(m_pk, m_sk);

 }

 

 void x25519::GeneratePrivateKey(RandomNumberGenerator &rng, byte *privateKey) const

 {

     rng.GenerateBlock(privateKey, SECRET_KEYLENGTH);

-    privateKey[0] &= 248; privateKey[31] &= 127; privateKey[31] |= 64;

+    ClampKey(privateKey);

 }

 

 void x25519::GeneratePublicKey(RandomNumberGenerator &rng, const byte *privateKey, byte *publicKey) const

 {

     CRYPTOPP_UNUSED(rng);

-    Donna::curve25519_mult(publicKey, privateKey);

+    SecretToPublicKey(publicKey, privateKey);

 }

 

 bool x25519::Agree(byte *agreedValue, const byte *privateKey, const byte *otherPublicKey, bool validateOtherPublicKey) const