Update documentation

1 files changed, 16 insertions, 9 deletions

diff --git a/xed25519.h b/xed25519.h
index 354d49ae..1f270174 100644
--- a/xed25519.h
+++ b/xed25519.h
@@ -249,7 +249,22 @@ protected:
 ///   digest the message incrementally. You should be careful with

 ///   large messages like files on-disk. The behavior is by design

 ///   because Bernstein feels small messages should be authenticated;

-///   and larger messages will be hashed by the application.

+///   and larger messages will be digested by the application.

+/// \details The accumulator is used for signing and verification.

+///   The first 64-bytes of storage is reserved for the signature.

+///   During signing the signature storage is unused. During

+///   verification the first 64 bytes holds the signature. The

+///   signature is provided by the PK_Verifier framework and the

+///   call to PK_Signer::InputSignature. Member functions data()

+///   and size() refer to the accumulated message. Member function

+///   signature() refers to the signature with an implicit size of

+///   SIGNATURE_LENGTH bytes.

+/// \details Applications which digest large messages, like an ISO

+///   disk file, should take care because the design effectively

+///   disgorges the format operation from the signing operation.

+///   Put another way, be careful to ensure what you are signing is

+///   is in fact a digest of the intended message, and not a different

+///   message digest supplied by an attacker.

 struct ed25519_MessageAccumulator : public PK_MessageAccumulator

 {

     CRYPTOPP_CONSTANT(RESERVE_SIZE=2048+64)

@@ -267,14 +282,6 @@ struct ed25519_MessageAccumulator : public PK_MessageAccumulator
         CRYPTOPP_UNUSED(rng); Restart();

     }

 

-    /// \brief Add data to the accumulator

-    /// \param msg pointer to the data to accumulate

-    /// \param len the size of the data, in bytes

-    void Update(const byte* msg, size_t len) {

-        if (msg && len)

-            m_msg.insert(m_msg.end(), msg, msg+len);

-    }

-

     /// \brief Reset the accumulator

     void Restart() {

         m_msg.reserve(RESERVE_SIZE);