Optimize FE1 format preserving encryption

Expose the state as the FPE_FE1 class which allows most values
to be precomputed. Approx 6-8 times faster.

1 files changed, 46 insertions, 6 deletions

diff --git a/src/lib/misc/fpe_fe1/fpe_fe1.h b/src/lib/misc/fpe_fe1/fpe_fe1.h
index 7f92f0601..a38231aa6 100644
--- a/src/lib/misc/fpe_fe1/fpe_fe1.h
+++ b/src/lib/misc/fpe_fe1/fpe_fe1.h
@@ -1,6 +1,6 @@
 /*
 * Format Preserving Encryption (FE1 scheme)
-* (C) 2009 Jack Lloyd
+* (C) 2009,2018 Jack Lloyd
 *
 * Botan is released under the Simplified BSD License (see license.txt)
 */
@@ -8,11 +8,51 @@
 #ifndef BOTAN_FPE_FE1_H_
 #define BOTAN_FPE_FE1_H_
 
+#include <botan/sym_algo.h>
 #include <botan/bigint.h>
-#include <botan/symkey.h>
+#include <botan/reducer.h>
 
 namespace Botan {
 
+class MessageAuthenticationCode;
+
+class BOTAN_PUBLIC_API(2,5) FPE_FE1 final : public SymmetricAlgorithm
+   {
+   public:
+      FPE_FE1(const BigInt& n,
+              size_t rounds = 3,
+              const std::string& mac_algo = "HMAC(SHA-256)");
+
+      Key_Length_Specification key_spec() const override;
+
+      std::string name() const;
+
+      void clear();
+
+      BigInt encrypt(const BigInt& x, const uint8_t tweak[], size_t tweak_len) const;
+
+      BigInt decrypt(const BigInt& x, const uint8_t tweak[], size_t tweak_len) const;
+
+      BigInt encrypt(const BigInt& x, uint64_t tweak) const;
+
+      BigInt decrypt(const BigInt& x, uint64_t tweak) const;
+   private:
+      void key_schedule(const uint8_t key[], size_t length) override;
+
+      BigInt F(const BigInt& R, size_t round,
+               const secure_vector<uint8_t>& tweak,
+               secure_vector<uint8_t>& tmp) const;
+
+      secure_vector<uint8_t> compute_tweak_mac(const uint8_t tweak[], size_t tweak_len) const;
+
+      std::unique_ptr<MessageAuthenticationCode> m_mac;
+      std::vector<uint8_t> m_n_bytes;
+      BigInt m_a;
+      BigInt m_b;
+      Modular_Reducer mod_a;
+      size_t m_rounds;
+   };
+
 namespace FPE {
 
 /**
@@ -27,8 +67,8 @@ namespace FPE {
 * @param tweak will modify the ciphertext (think of as an IV)
 */
 BigInt BOTAN_PUBLIC_API(2,0) fe1_encrypt(const BigInt& n, const BigInt& X,
-                             const SymmetricKey& key,
-                             const std::vector<uint8_t>& tweak);
+                                         const SymmetricKey& key,
+                                         const std::vector<uint8_t>& tweak);
 
 /**
 * Decrypt X from and onto the group Z_n using key and tweak
@@ -38,8 +78,8 @@ BigInt BOTAN_PUBLIC_API(2,0) fe1_encrypt(const BigInt& n, const BigInt& X,
 * @param tweak the same tweak used for encryption
 */
 BigInt BOTAN_PUBLIC_API(2,0) fe1_decrypt(const BigInt& n, const BigInt& X,
-                             const SymmetricKey& key,
-                             const std::vector<uint8_t>& tweak);
+                                         const SymmetricKey& key,
+                                         const std::vector<uint8_t>& tweak);
 
 }