1 files changed, 62 insertions, 0 deletions
diff --git a/lib/prf/hkdf/hkdf.cpp b/lib/prf/hkdf/hkdf.cpp
new file mode 100644
index 000000000..0a1f7cb31
--- /dev/null
+++ b/lib/prf/hkdf/hkdf.cpp
@@ -0,0 +1,62 @@
+/*
+* HKDF
+* (C) 2013 Jack Lloyd
+*
+* Distributed under the terms of the Botan license
+*/
+
+#include <botan/hkdf.h>
+
+namespace Botan {
+
+std::string HKDF::name() const
+   {
+   return "HKDF(" + m_prf->name() + ")";
+   }
+
+void HKDF::clear()
+   {
+   m_extractor->clear();
+   m_prf->clear();
+   }
+
+void HKDF::start_extract(const byte salt[], size_t salt_len)
+   {
+   m_extractor->set_key(salt, salt_len);
+   }
+
+void HKDF::extract(const byte input[], size_t input_len)
+   {
+   m_extractor->update(input, input_len);
+   }
+
+void HKDF::finish_extract()
+   {
+   m_prf->set_key(m_extractor->final());
+   }
+
+void HKDF::expand(byte output[], size_t output_len,
+                  const byte info[], size_t info_len)
+   {
+   if(output_len > m_prf->output_length() * 255)
+      throw std::invalid_argument("HKDF requested output too large");
+
+   byte counter = 1;
+
+   secure_vector<byte> T;
+
+   while(output_len)
+      {
+      m_prf->update(T);
+      m_prf->update(info, info_len);
+      m_prf->update(counter++);
+      T = m_prf->final();
+
+      const size_t to_write = std::min(T.size(), output_len);
+      copy_mem(&output[0], &T[0], to_write);
+      output += to_write;
+      output_len -= to_write;
+      }
+   }
+
+}