Enable extended output in SHAKE-128 and SHAKE-256 (GH #805, PR #806)

1 files changed, 20 insertions, 2 deletions

diff --git a/shake.cpp b/shake.cpp
index aa880389..65e08235 100644
--- a/shake.cpp
+++ b/shake.cpp
@@ -52,6 +52,13 @@ void SHAKE::Restart()
     m_counter = 0;

 }

 

+void SHAKE::ThrowIfInvalidTruncatedSize(size_t size) const

+{

+	if (size > UINT_MAX)

+		throw InvalidArgument(std::string("HashTransformation: can't truncate a ") +

+		    IntToString(UINT_MAX) + " byte digest to " + IntToString(size) + " bytes");

+}

+

 void SHAKE::TruncatedFinal(byte *hash, size_t size)

 {

     CRYPTOPP_ASSERT(hash != NULLPTR);

@@ -59,8 +66,19 @@ void SHAKE::TruncatedFinal(byte *hash, size_t size)
 

     m_state.BytePtr()[m_counter] ^= 0x1F;

     m_state.BytePtr()[r()-1] ^= 0x80;

-    KeccakF1600(m_state);

-    std::memcpy(hash, m_state, size);

+

+    // FIPS 202, Algorithm 8, pp 18-19.

+    while (size > 0)

+    {

+        KeccakF1600(m_state);

+

+        const size_t segmentLen = STDMIN(size, (size_t)BlockSize());

+        std::memcpy(hash, m_state, segmentLen);

+

+        hash += segmentLen;

+        size -= segmentLen;

+    }

+

     Restart();

 }