Implicit rounds based on key variable size

4 files changed, 44 insertions, 27 deletions

diff --git a/src/block/rc5/rc5.cpp b/src/block/rc5/rc5.cpp
index 86777f772..d9e74683c 100644
--- a/src/block/rc5/rc5.cpp
+++ b/src/block/rc5/rc5.cpp
@@ -18,20 +18,25 @@ namespace Botan {
 */
 void RC5::encrypt_n(const byte in[], byte out[], size_t blocks) const
    {
+   const size_t rounds = (S.size() - 2) / 2;
+
    for(size_t i = 0; i != blocks; ++i)
       {
       u32bit A = load_le<u32bit>(in, 0);
       u32bit B = load_le<u32bit>(in, 1);
 
       A += S[0]; B += S[1];
-      for(size_t j = 0; j != ROUNDS; j += 4)
+      for(size_t j = 0; j != rounds; j += 4)
          {
          A = rotate_left(A ^ B, B % 32) + S[2*j+2];
          B = rotate_left(B ^ A, A % 32) + S[2*j+3];
+
          A = rotate_left(A ^ B, B % 32) + S[2*j+4];
          B = rotate_left(B ^ A, A % 32) + S[2*j+5];
+
          A = rotate_left(A ^ B, B % 32) + S[2*j+6];
          B = rotate_left(B ^ A, A % 32) + S[2*j+7];
+
          A = rotate_left(A ^ B, B % 32) + S[2*j+8];
          B = rotate_left(B ^ A, A % 32) + S[2*j+9];
          }
@@ -48,19 +53,24 @@ void RC5::encrypt_n(const byte in[], byte out[], size_t blocks) const
 */
 void RC5::decrypt_n(const byte in[], byte out[], size_t blocks) const
    {
+   const size_t rounds = (S.size() - 2) / 2;
+
    for(size_t i = 0; i != blocks; ++i)
       {
       u32bit A = load_le<u32bit>(in, 0);
       u32bit B = load_le<u32bit>(in, 1);
 
-      for(size_t j = ROUNDS; j != 0; j -= 4)
+      for(size_t j = rounds; j != 0; j -= 4)
          {
          B = rotate_right(B - S[2*j+1], A % 32) ^ A;
          A = rotate_right(A - S[2*j  ], B % 32) ^ B;
+
          B = rotate_right(B - S[2*j-1], A % 32) ^ A;
          A = rotate_right(A - S[2*j-2], B % 32) ^ B;
+
          B = rotate_right(B - S[2*j-3], A % 32) ^ A;
          A = rotate_right(A - S[2*j-4], B % 32) ^ B;
+
          B = rotate_right(B - S[2*j-5], A % 32) ^ A;
          A = rotate_right(A - S[2*j-6], B % 32) ^ B;
          }
@@ -106,19 +116,19 @@ void RC5::key_schedule(const byte key[], size_t length)
 */
 std::string RC5::name() const
    {
-   return "RC5(" + to_string(ROUNDS) + ")";
+   return "RC5(" + to_string(get_rounds()) + ")";
    }
 
 /*
 * RC5 Constructor
 */
-RC5::RC5(size_t r) :
-   BlockCipher_Fixed_Block_Size(1, 32),
-   ROUNDS(r)
+RC5::RC5(size_t rounds) : BlockCipher_Fixed_Block_Size(1, 32)
    {
-   if(ROUNDS < 8 || ROUNDS > 32 || (ROUNDS % 4 != 0))
-      throw Invalid_Argument(name() + ": Invalid number of rounds");
-   S.resize(2*ROUNDS + 2);
+   if(rounds < 8 || rounds > 32 || (rounds % 4 != 0))
+      throw Invalid_Argument("RC5: Invalid number of rounds " +
+                             to_string(rounds));
+
+   S.resize(2*rounds + 2);
    }
 
 }
diff --git a/src/block/rc5/rc5.h b/src/block/rc5/rc5.h
index a9f3b5b0e..cb282af4e 100644
--- a/src/block/rc5/rc5.h
+++ b/src/block/rc5/rc5.h
@@ -23,7 +23,7 @@ class BOTAN_DLL RC5 : public BlockCipher_Fixed_Block_Size<8>
 
       void clear() { zeroise(S); }
       std::string name() const;
-      BlockCipher* clone() const { return new RC5(ROUNDS); }
+      BlockCipher* clone() const { return new RC5(get_rounds()); }
 
       /**
       * @param rounds the number of RC5 rounds to run. Must be between
@@ -31,9 +31,11 @@ class BOTAN_DLL RC5 : public BlockCipher_Fixed_Block_Size<8>
       */
       RC5(size_t rounds);
    private:
+      size_t get_rounds() const { return (S.size() - 2) / 2; }
+
       void key_schedule(const byte[], size_t);
+
       SecureVector<u32bit> S;
-      const size_t ROUNDS;
    };
 
 }
diff --git a/src/block/safer/safer_sk.cpp b/src/block/safer/safer_sk.cpp
index cd9dddf34..941c4fed8 100644
--- a/src/block/safer/safer_sk.cpp
+++ b/src/block/safer/safer_sk.cpp
@@ -17,12 +17,14 @@ namespace Botan {
 */
 void SAFER_SK::encrypt_n(const byte in[], byte out[], size_t blocks) const
    {
+   const size_t rounds = get_rounds();
+
    for(size_t i = 0; i != blocks; ++i)
       {
       byte A = in[0], B = in[1], C = in[2], D = in[3],
            E = in[4], F = in[5], G = in[6], H = in[7], X, Y;
 
-      for(size_t j = 0; j != 16*ROUNDS; j += 16)
+      for(size_t j = 0; j != 16*rounds; j += 16)
          {
          A = EXP[A ^ EK[j  ]]; B = LOG[B + EK[j+1]];
          C = LOG[C + EK[j+2]]; D = EXP[D ^ EK[j+3]];
@@ -38,10 +40,10 @@ void SAFER_SK::encrypt_n(const byte in[], byte out[], size_t blocks) const
          A += B; F = C + G; E = C + F; C = X; G = Y;
          }
 
-      out[0] = A ^ EK[16*ROUNDS+0]; out[1] = B + EK[16*ROUNDS+1];
-      out[2] = C + EK[16*ROUNDS+2]; out[3] = D ^ EK[16*ROUNDS+3];
-      out[4] = E ^ EK[16*ROUNDS+4]; out[5] = F + EK[16*ROUNDS+5];
-      out[6] = G + EK[16*ROUNDS+6]; out[7] = H ^ EK[16*ROUNDS+7];
+      out[0] = A ^ EK[16*rounds+0]; out[1] = B + EK[16*rounds+1];
+      out[2] = C + EK[16*rounds+2]; out[3] = D ^ EK[16*rounds+3];
+      out[4] = E ^ EK[16*rounds+4]; out[5] = F + EK[16*rounds+5];
+      out[6] = G + EK[16*rounds+6]; out[7] = H ^ EK[16*rounds+7];
 
       in += BLOCK_SIZE;
       out += BLOCK_SIZE;
@@ -53,16 +55,18 @@ void SAFER_SK::encrypt_n(const byte in[], byte out[], size_t blocks) const
 */
 void SAFER_SK::decrypt_n(const byte in[], byte out[], size_t blocks) const
    {
+   const size_t rounds = get_rounds();
+
    for(size_t i = 0; i != blocks; ++i)
       {
       byte A = in[0], B = in[1], C = in[2], D = in[3],
            E = in[4], F = in[5], G = in[6], H = in[7];
 
-      A ^= EK[16*ROUNDS+0]; B -= EK[16*ROUNDS+1]; C -= EK[16*ROUNDS+2];
-      D ^= EK[16*ROUNDS+3]; E ^= EK[16*ROUNDS+4]; F -= EK[16*ROUNDS+5];
-      G -= EK[16*ROUNDS+6]; H ^= EK[16*ROUNDS+7];
+      A ^= EK[16*rounds+0]; B -= EK[16*rounds+1]; C -= EK[16*rounds+2];
+      D ^= EK[16*rounds+3]; E ^= EK[16*rounds+4]; F -= EK[16*rounds+5];
+      G -= EK[16*rounds+6]; H ^= EK[16*rounds+7];
 
-      for(s32bit j = 16*(ROUNDS-1); j >= 0; j -= 16)
+      for(s32bit j = 16*(rounds-1); j >= 0; j -= 16)
          {
          byte T = E; E = B; B = C; C = T; T = F; F = D; D = G; G = T;
          A -= E; B -= F; C -= G; D -= H; E -= A; F -= B; G -= C; H -= D;
@@ -99,7 +103,7 @@ void SAFER_SK::key_schedule(const byte key[], size_t)
       KB[17] ^= KB[i+9] = EK[i] = key[i+8];
       }
 
-   for(size_t i = 0; i != ROUNDS; ++i)
+   for(size_t i = 0; i != get_rounds(); ++i)
       {
       for(size_t j = 0; j != 18; ++j)
          KB[j] = rotate_left(KB[j], 6);
@@ -113,7 +117,7 @@ void SAFER_SK::key_schedule(const byte key[], size_t)
 */
 std::string SAFER_SK::name() const
    {
-   return "SAFER-SK(" + to_string(ROUNDS) + ")";
+   return "SAFER-SK(" + to_string(get_rounds()) + ")";
    }
 
 /*
@@ -121,18 +125,19 @@ std::string SAFER_SK::name() const
 */
 BlockCipher* SAFER_SK::clone() const
    {
-   return new SAFER_SK(ROUNDS);
+   return new SAFER_SK(get_rounds());
    }
 
 /*
 * SAFER-SK Constructor
 */
 SAFER_SK::SAFER_SK(size_t rounds) :
-   BlockCipher_Fixed_Block_Size(16),
-   EK(16 * rounds + 8), ROUNDS(rounds)
+   BlockCipher_Fixed_Block_Size(16)
    {
-   if(ROUNDS > 13 || ROUNDS == 0)
+   if(rounds > 13 || rounds == 0)
       throw Invalid_Argument(name() + ": Invalid number of rounds");
+
+   EK.resize(16 * rounds + 8);
    }
 
 }
diff --git a/src/block/safer/safer_sk.h b/src/block/safer/safer_sk.h
index 5e8d32b0a..2fde757bd 100644
--- a/src/block/safer/safer_sk.h
+++ b/src/block/safer/safer_sk.h
@@ -31,6 +31,7 @@ class BOTAN_DLL SAFER_SK : public BlockCipher_Fixed_Block_Size<8>
       */
       SAFER_SK(size_t rounds);
    private:
+      size_t get_rounds() const { return (EK.size() - 8) / 16; }
       void key_schedule(const byte[], size_t);
 
       static const byte EXP[256];
@@ -39,7 +40,6 @@ class BOTAN_DLL SAFER_SK : public BlockCipher_Fixed_Block_Size<8>
       static const byte KEY_INDEX[208];
 
       SecureVector<byte> EK;
-      const size_t ROUNDS;
    };
 
 }