1 files changed, 112 insertions, 0 deletions
diff --git a/modules/pk_pad/emsa1/emsa1.cpp b/modules/pk_pad/emsa1/emsa1.cpp
new file mode 100644
index 000000000..8977356e8
--- /dev/null
+++ b/modules/pk_pad/emsa1/emsa1.cpp
@@ -0,0 +1,112 @@
+/*************************************************
+* EMSA1 Source File                              *
+* (C) 1999-2007 Jack Lloyd                       *
+*************************************************/
+
+#include <botan/emsa.h>
+#include <botan/lookup.h>
+
+namespace Botan {
+
+namespace {
+
+SecureVector<byte> emsa1_encoding(const MemoryRegion<byte>& msg,
+                                  u32bit output_bits)
+   {
+   if(8*msg.size() <= output_bits)
+      return msg;
+
+   u32bit shift = 8*msg.size() - output_bits;
+
+   u32bit byte_shift = shift / 8, bit_shift = shift % 8;
+   SecureVector<byte> digest(msg.size() - byte_shift);
+
+   for(u32bit j = 0; j != msg.size() - byte_shift; ++j)
+      digest[j] = msg[j];
+
+   if(bit_shift)
+      {
+      byte carry = 0;
+      for(u32bit j = 0; j != digest.size(); ++j)
+         {
+         byte temp = digest[j];
+         digest[j] = (temp >> bit_shift) | carry;
+         carry = (temp << (8 - bit_shift));
+         }
+      }
+   return digest;
+   }
+
+}
+
+/*************************************************
+* EMSA1 Update Operation                         *
+*************************************************/
+void EMSA1::update(const byte input[], u32bit length)
+   {
+   hash->update(input, length);
+   }
+
+/*************************************************
+* Return the raw (unencoded) data                *
+*************************************************/
+SecureVector<byte> EMSA1::raw_data()
+   {
+   return hash->final();
+   }
+
+/*************************************************
+* EMSA1 Encode Operation                         *
+*************************************************/
+SecureVector<byte> EMSA1::encoding_of(const MemoryRegion<byte>& msg,
+                                      u32bit output_bits,
+                                      RandomNumberGenerator&)
+   {
+   if(msg.size() != hash->OUTPUT_LENGTH)
+      throw Encoding_Error("EMSA1::encoding_of: Invalid size for input");
+   return emsa1_encoding(msg, output_bits);
+   }
+
+/*************************************************
+* EMSA1 Decode/Verify Operation                  *
+*************************************************/
+bool EMSA1::verify(const MemoryRegion<byte>& coded,
+                   const MemoryRegion<byte>& raw, u32bit key_bits) throw()
+   {
+   try {
+      if(raw.size() != hash->OUTPUT_LENGTH)
+         throw Encoding_Error("EMSA1::encoding_of: Invalid size for input");
+
+      SecureVector<byte> our_coding = emsa1_encoding(raw, key_bits);
+
+      if(our_coding == coded) return true;
+      if(our_coding[0] != 0) return false;
+      if(our_coding.size() <= coded.size()) return false;
+
+      u32bit offset = 0;
+      while(our_coding[offset] == 0 && offset < our_coding.size())
+         ++offset;
+      if(our_coding.size() - offset != coded.size())
+         return false;
+
+      for(u32bit j = 0; j != coded.size(); ++j)
+         if(coded[j] != our_coding[j+offset])
+            return false;
+
+      return true;
+      }
+   catch(Invalid_Argument)
+      {
+      return false;
+      }
+   }
+
+/*************************************************
+* EMSA1 Constructor                              *
+*************************************************/
+EMSA1::EMSA1(const std::string& hash_name) :
+   hash(get_hash(hash_name))
+   {
+   }
+
+}