From 67fc02d47f52987df5060142782d1aea2dd65436 Mon Sep 17 00:00:00 2001
From: lloyd <lloyd@randombit.net>
Date: Wed, 24 Sep 2008 12:49:29 +0000
Subject: Add an example database row encryptor

---
 doc/examples/row_encryptor.cpp | 134 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 134 insertions(+)
 create mode 100644 doc/examples/row_encryptor.cpp

(limited to 'doc/examples/row_encryptor.cpp')

diff --git a/doc/examples/row_encryptor.cpp b/doc/examples/row_encryptor.cpp
new file mode 100644
index 000000000..dc15ee6c4
--- /dev/null
+++ b/doc/examples/row_encryptor.cpp
@@ -0,0 +1,134 @@
+#include <string>
+#include <memory>
+#include <sstream>
+#include <iostream>
+
+#include <botan/botan.h>
+#include <botan/filters.h>
+#include <botan/eax.h>
+
+using namespace Botan;
+
+/**
+Encrypt and decrypt small rows
+*/
+class Row_Encryptor
+   {
+   public:
+      Row_Encryptor(const std::string& passphrase,
+                    RandomNumberGenerator& rng);
+
+      std::string encrypt(const std::string& input,
+                          const MemoryRegion<byte>& salt);
+
+      std::string decrypt(const std::string& input,
+                          const MemoryRegion<byte>& salt);
+
+   private:
+      Row_Encryptor(const Row_Encryptor&) {}
+      Row_Encryptor& operator=(const Row_Encryptor&) { return (*this); }
+
+      Pipe enc_pipe, dec_pipe;
+      EAX_Encryption* eax_enc; // owned by enc_pipe
+      EAX_Decryption* eax_dec; // owned by dec_pipe;
+   };
+
+Row_Encryptor::Row_Encryptor(const std::string& passphrase,
+                             RandomNumberGenerator& rng)
+   {
+   std::auto_ptr<S2K> s2k(get_s2k("PBKDF2(SHA-160)"));
+
+   s2k->set_iterations(10000);
+
+   s2k->new_random_salt(rng, 10); // 10 bytes == 80 bits
+
+   SecureVector<byte> key = s2k->derive_key(32, passphrase).bits_of();
+
+   /*
+    Save pointers to the EAX objects so we can change the IV as needed
+   */
+   enc_pipe.append(eax_enc = new EAX_Encryption("Serpent"));
+   dec_pipe.append(eax_dec = new EAX_Decryption("Serpent"));
+
+   eax_enc->set_key(key);
+   eax_dec->set_key(key);
+   }
+
+std::string Row_Encryptor::encrypt(const std::string& input,
+                                   const MemoryRegion<byte>& salt)
+   {
+   eax_enc->set_iv(salt);
+
+   enc_pipe.start_msg();
+   enc_pipe.write(input);
+   enc_pipe.end_msg();
+
+   return enc_pipe.read_all_as_string(Pipe::LAST_MESSAGE);
+   }
+
+std::string Row_Encryptor::decrypt(const std::string& input,
+                                   const MemoryRegion<byte>& salt)
+   {
+   eax_dec->set_iv(salt);
+
+   dec_pipe.start_msg();
+   dec_pipe.write(input);
+   dec_pipe.end_msg();
+
+   return dec_pipe.read_all_as_string(Pipe::LAST_MESSAGE);
+   }
+
+/*************************
+  Test code follows:
+*/
+
+#include <botan/loadstor.h>
+
+int main()
+   {
+   LibraryInitializer init;
+
+   std::auto_ptr<RandomNumberGenerator> rng(RandomNumberGenerator::make_rng());
+
+   Row_Encryptor encryptor("secret passphrase", *rng);
+
+   std::vector<std::string> original_inputs;
+
+   for(u32bit i = 0; i != 15000; ++i)
+      {
+      std::ostringstream out;
+
+      // This will actually generate variable length inputs (when
+      // there are leading 0s, which are skipped), which is good
+      // since it assures performance is OK across a mix of lengths
+      // TODO: Maybe randomize the length slightly?
+
+      for(u32bit j = 0; j != 32; ++j)
+         out << std::hex << (int)rng->next_byte();
+
+      original_inputs.push_back(out.str());
+      }
+
+   std::vector<std::string> encrypted_values;
+   MemoryVector<byte> salt(4); // keep out of loop to avoid excessive dynamic allocation
+
+   for(u32bit i = 0; i != original_inputs.size(); ++i)
+      {
+      std::string input = original_inputs[i];
+      store_le(i, salt);
+
+      encrypted_values.push_back(encryptor.encrypt(input, salt));
+      }
+
+   for(u32bit i = 0; i != encrypted_values.size(); ++i)
+      {
+      std::string ciphertext = encrypted_values[i];
+      store_le(i, salt); // NOTE: same salt value as previous loop (index value)
+
+      std::string output = encryptor.decrypt(ciphertext, salt);
+
+      if(output != original_inputs[i])
+         std::cout << "BOOM " << i << "\n";
+      }
+
+   }
-- 
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