Show as creating an engine instead

1 files changed, 100 insertions, 0 deletions

diff --git a/doc/examples/new_engine.cpp b/doc/examples/new_engine.cpp
new file mode 100644
index 000000000..2f412a6b9
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+++ b/doc/examples/new_engine.cpp
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+/*
+* Adding an application specific engine
+* (C) 2004,2008 Jack Lloyd
+*
+* Distributed under the terms of the Botan license
+*/
+
+#include <botan/stream_cipher.h>
+#include <botan/engine.h>
+
+using namespace Botan;
+
+class XOR_Cipher : public StreamCipher
+   {
+   public:
+      void clear() throw() { mask.destroy(); mask_pos = 0; }
+
+      // what we want to call this cipher
+      std::string name() const { return "XOR"; }
+
+      // return a new object of this type
+      StreamCipher* clone() const { return new XOR_Cipher; }
+
+      XOR_Cipher() : StreamCipher(1, 32) { mask_pos = 0; }
+   private:
+      void cipher(const byte in[], byte out[], u32bit length)
+         {
+         for(u32bit j = 0; j != length; j++)
+            {
+            out[j] = in[j] ^ mask[mask_pos];
+            mask_pos = (mask_pos + 1) % mask.size();
+            }
+         }
+
+      void key_schedule(const byte key[], u32bit length)
+         {
+         mask.set(key, length);
+         }
+
+      SecureVector<byte> mask;
+      u32bit mask_pos;
+   };
+
+class Application_Engine : public Engine
+   {
+   public:
+      std::string provider_name() const { return "application"; }
+
+      StreamCipher* find_stream_cipher(const SCAN_Name& request,
+                                       Algorithm_Factory&) const
+         {
+         if(request.algo_name() == "XOR")
+            return new XOR_Cipher;
+         return 0;
+         }
+   };
+
+#include <botan/botan.h>
+#include <iostream>
+#include <string>
+
+int main()
+   {
+
+   Botan::LibraryInitializer init;
+
+   global_state().algorithm_factory().add_engine(
+      new Application_Engine);
+
+   // a hex key value
+   SymmetricKey key("010203040506070809101112AAFF");
+
+   /*
+    Since stream ciphers are typically additive, the encryption and
+    decryption ops are the same, so this isn't terribly interesting.
+
+    If this where a block cipher you would have to add a cipher mode and
+    padding method, such as "/CBC/PKCS7".
+   */
+   Pipe enc(get_cipher("XOR", key, ENCRYPTION), new Hex_Encoder);
+   Pipe dec(new Hex_Decoder, get_cipher("XOR", key, DECRYPTION));
+
+   // I think the pigeons are actually asleep at midnight...
+   std::string secret = "The pigeon flys at midnight.";
+
+   std::cout << "The secret message is '" << secret << "'" << std::endl;
+
+   enc.process_msg(secret);
+   std::string cipher = enc.read_all_as_string();
+
+   std::cout << "The encrypted secret message is " << cipher << std::endl;
+
+   dec.process_msg(cipher);
+   secret = dec.read_all_as_string();
+
+   std::cout << "The decrypted secret message is '"
+             << secret << "'" << std::endl;
+
+   return 0;
+   }