diff options
| -rw-r--r-- | src/lib/block/idea/idea.cpp | 9 | ||||
| -rw-r--r-- | src/lib/utils/ct_utils.h | 41 |
2 files changed, 24 insertions, 26 deletions
diff --git a/src/lib/block/idea/idea.cpp b/src/lib/block/idea/idea.cpp index ffd1bf56a..de153e2c5 100644 --- a/src/lib/block/idea/idea.cpp +++ b/src/lib/block/idea/idea.cpp @@ -20,8 +20,7 @@ namespace { inline uint16_t mul(uint16_t x, uint16_t y) { const uint32_t P = static_cast<uint32_t>(x) * y; - - const uint16_t Z_mask = static_cast<uint16_t>(CT::expand_mask(P) & 0xFFFF); + const uint16_t P_mask = static_cast<uint16_t>(CT::is_zero(P) & 0xFFFF); const uint32_t P_hi = P >> 16; const uint32_t P_lo = P & 0xFFFF; @@ -30,7 +29,7 @@ inline uint16_t mul(uint16_t x, uint16_t y) const uint16_t r_1 = static_cast<uint16_t>((P_lo - P_hi) + carry); const uint16_t r_2 = 1 - x - y; - return CT::select(Z_mask, r_1, r_2); + return CT::select(P_mask, r_2, r_1); } /* @@ -80,10 +79,10 @@ void idea_op(const uint8_t in[], uint8_t out[], size_t blocks, const uint16_t K[ X3 += K[6*j+2]; X4 = mul(X4, K[6*j+3]); - uint16_t T0 = X3; + const uint16_t T0 = X3; X3 = mul(X3 ^ X1, K[6*j+4]); - uint16_t T1 = X2; + const uint16_t T1 = X2; X2 = mul((X2 ^ X4) + X3, K[6*j+5]); X3 += X2; diff --git a/src/lib/utils/ct_utils.h b/src/lib/utils/ct_utils.h index 013267874..4fd06ec3d 100644 --- a/src/lib/utils/ct_utils.h +++ b/src/lib/utils/ct_utils.h @@ -15,6 +15,7 @@ #define BOTAN_TIMING_ATTACK_CM_H_ #include <botan/secmem.h> +#include <type_traits> #include <vector> #if defined(BOTAN_HAS_VALGRIND) @@ -74,6 +75,22 @@ inline void unpoison(T& p) #endif } +/* Mask generation */ + +template<typename T> +inline T expand_top_bit(T a) + { + static_assert(std::is_unsigned<T>::value, "unsigned integer type required"); + return static_cast<T>(0) - (a >> (sizeof(T)*8-1)); + } + +template<typename T> +inline T is_zero(T x) + { + static_assert(std::is_unsigned<T>::value, "unsigned integer type required"); + return expand_top_bit<T>(~x & (x - 1)); + } + /* * T should be an unsigned machine integer type * Expand to a mask used for other operations @@ -85,26 +102,14 @@ inline void unpoison(T& p) template<typename T> inline T expand_mask(T x) { - T r = x; - // First fold r down to a single bit - for(size_t i = 1; i != sizeof(T)*8; i *= 2) - { - r = r | static_cast<T>(r >> i); - } - r &= 1; - r = static_cast<T>(~(r - 1)); - return r; - } - -template<typename T> -inline T expand_top_bit(T a) - { - return expand_mask<T>(a >> (sizeof(T)*8-1)); + static_assert(std::is_unsigned<T>::value, "unsigned integer type required"); + return ~is_zero(x); } template<typename T> inline T select(T mask, T from0, T from1) { + static_assert(std::is_unsigned<T>::value, "unsigned integer type required"); return static_cast<T>((from0 & mask) | (from1 & ~mask)); } @@ -127,12 +132,6 @@ inline ValT val_or_zero(PredT pred_val, ValT val) } template<typename T> -inline T is_zero(T x) - { - return static_cast<T>(~expand_mask(x)); - } - -template<typename T> inline T is_equal(T x, T y) { return is_zero<T>(x ^ y); |