1 files changed, 175 insertions, 0 deletions
diff --git a/doc/examples/encrypt.cpp b/doc/examples/encrypt.cpp
new file mode 100644
index 000000000..c2cf2c5ba
--- /dev/null
+++ b/doc/examples/encrypt.cpp
@@ -0,0 +1,175 @@
+/*
+Encrypt a file using a block cipher in CBC mode. Compresses the plaintext
+with Zlib, MACs with HMAC(SHA-1). Stores the block cipher used in the file,
+so you don't have to specify it when decrypting.
+
+What a real application would do (and what this example should do), is test for
+the presence of the Zlib module, and use it only if it's available. Then add
+some marker to the stream so the other side knows whether or not the plaintext
+was compressed. Bonus points for supporting multiple compression schemes.
+
+Another flaw is that is stores the entire ciphertext in memory, so if the file
+you're encrypting is 1 Gb... you better have a lot of RAM.
+
+Based on the base64 example, of all things
+
+Written by Jack Lloyd ([email protected]) on August 5, 2002
+
+This file is in the public domain
+*/
+#include <fstream>
+#include <iostream>
+#include <string>
+#include <vector>
+#include <cstring>
+
+#include <botan/botan.h>
+
+#if defined(BOTAN_EXT_COMPRESSOR_ZLIB)
+  #include <botan/zlib.h>
+#else
+  #error "You didn't compile the zlib module into Botan"
+#endif
+
+using namespace Botan;
+
+std::string b64_encode(const SecureVector<byte>&);
+
+int main(int argc, char* argv[])
+   {
+   if(argc < 2)
+      {
+      std::cout << "Usage: " << argv[0] << " [-c algo] -p passphrase file\n"
+                   "   -p : Use this passphrase to encrypt\n"
+                   "   -c : Encrypt with block cipher 'algo' (default 3DES)\n";
+      return 1;
+      }
+
+   std::string algo = "TripleDES";
+   std::string filename, passphrase;
+
+   // Holy hell, argument processing is a PITA
+   for(int j = 1; argv[j] != 0; j++)
+      {
+      if(std::strcmp(argv[j], "-c") == 0)
+         {
+         if(argv[j+1])
+            {
+            algo = argv[j+1];
+            j++;
+            }
+         else
+            {
+            std::cout << "No argument for -c option" << std::endl;
+            return 1;
+            }
+         }
+      else if(std::strcmp(argv[j], "-p") == 0)
+         {
+         if(argv[j+1])
+            {
+            passphrase = argv[j+1];
+            j++;
+            }
+         else
+            {
+            std::cout << "No argument for -p option" << std::endl;
+            return 1;
+            }
+         }
+      else
+         {
+         if(filename != "")
+            {
+            std::cout << "You can only specify one file at a time\n";
+            return 1;
+            }
+         filename = argv[j];
+         }
+      }
+
+   if(passphrase == "")
+      {
+      std::cout << "You have to specify a passphrase!" << std::endl;
+      return 1;
+      }
+
+   std::ifstream in(filename.c_str());
+   if(!in)
+      {
+      std::cout << "ERROR: couldn't open " << filename << std::endl;
+      return 1;
+      }
+
+   std::string outfile = filename + ".enc";
+   std::ofstream out(outfile.c_str());
+   if(!out)
+      {
+      std::cout << "ERROR: couldn't open " << outfile << std::endl;
+      return 1;
+      }
+
+   try {
+
+   LibraryInitializer init;
+
+   if(!have_block_cipher(algo))
+      {
+      std::cout << "Don't know about the block cipher \"" << algo << "\"\n";
+      return 1;
+      }
+
+   const u32bit key_len = max_keylength_of(algo);
+   const u32bit iv_len = block_size_of(algo);
+
+   std::auto_ptr<S2K> s2k(get_s2k("PBKDF2(SHA-1)"));
+   s2k->set_iterations(8192);
+   s2k->new_random_salt(8);
+
+   SymmetricKey bc_key = s2k->derive_key(key_len, "BLK" + passphrase);
+   InitializationVector iv = s2k->derive_key(iv_len, "IVL" + passphrase);
+   SymmetricKey mac_key = s2k->derive_key(16, "MAC" + passphrase);
+
+   // Just to be all fancy we even write a (simple) header.
+   out << "-------- ENCRYPTED FILE --------" << std::endl;
+   out << algo << std::endl;
+   out << b64_encode(s2k->current_salt()) << std::endl;
+
+   Pipe pipe(new Fork(
+                new Chain(new MAC_Filter("HMAC(SHA-1)", mac_key),
+                          new Base64_Encoder
+                   ),
+                new Chain(new Zlib_Compression,
+                          get_cipher(algo + "/CBC", bc_key, iv, ENCRYPTION),
+                          new Base64_Encoder(true)
+                   )
+                )
+      );
+
+   pipe.start_msg();
+   in >> pipe;
+   pipe.end_msg();
+
+   out << pipe.read_all_as_string(0) << std::endl;
+   out << pipe.read_all_as_string(1);
+
+   }
+   catch(Algorithm_Not_Found)
+      {
+      std::cout << "Don't know about the block cipher \"" << algo << "\"\n";
+      return 1;
+      }
+   catch(std::exception& e)
+      {
+      std::cout << "Exception caught: " << e.what() << std::endl;
+      return 1;
+      }
+   return 0;
+   }
+
+std::string b64_encode(const SecureVector<byte>& in)
+   {
+   Pipe pipe(new Base64_Encoder);
+   pipe.process_msg(in);
+   return pipe.read_all_as_string();
+   }