diff options
Diffstat (limited to 'lib/libcrypto/bn/bn_lcl.h')
| -rw-r--r-- | lib/libcrypto/bn/bn_lcl.h | 39 |
1 files changed, 39 insertions, 0 deletions
diff --git a/lib/libcrypto/bn/bn_lcl.h b/lib/libcrypto/bn/bn_lcl.h index 253e195e238..a84998f2bd4 100644 --- a/lib/libcrypto/bn/bn_lcl.h +++ b/lib/libcrypto/bn/bn_lcl.h @@ -177,6 +177,45 @@ struct bignum_ctx +/* BN_mod_exp_mont_conttime is based on the assumption that the + * L1 data cache line width of the target processor is at least + * the following value. + */ +#define MOD_EXP_CTIME_MIN_CACHE_LINE_WIDTH ( 64 ) +#define MOD_EXP_CTIME_MIN_CACHE_LINE_MASK (MOD_EXP_CTIME_MIN_CACHE_LINE_WIDTH - 1) + +/* Window sizes optimized for fixed window size modular exponentiation + * algorithm (BN_mod_exp_mont_consttime). + * + * To achieve the security goals of BN_mode_exp_mont_consttime, the + * maximum size of the window must not exceed + * log_2(MOD_EXP_CTIME_MIN_CACHE_LINE_WIDTH). + * + * Window size thresholds are defined for cache line sizes of 32 and 64, + * cache line sizes where log_2(32)=5 and log_2(64)=6 respectively. A + * window size of 7 should only be used on processors that have a 128 + * byte or greater cache line size. + */ +#if MOD_EXP_CTIME_MIN_CACHE_LINE_WIDTH == 64 + +# define BN_window_bits_for_ctime_exponent_size(b) \ + ((b) > 937 ? 6 : \ + (b) > 306 ? 5 : \ + (b) > 89 ? 4 : \ + (b) > 22 ? 3 : 1) +# define BN_MAX_WINDOW_BITS_FOR_CTIME_EXPONENT_SIZE (6) + +#elif MOD_EXP_CTIME_MIN_CACHE_LINE_WIDTH == 32 + +# define BN_window_bits_for_ctime_exponent_size(b) \ + ((b) > 306 ? 5 : \ + (b) > 89 ? 4 : \ + (b) > 22 ? 3 : 1) +# define BN_MAX_WINDOW_BITS_FOR_CTIME_EXPONENT_SIZE (5) + +#endif + + /* Pentium pro 16,16,16,32,64 */ /* Alpha 16,16,16,16.64 */ #define BN_MULL_SIZE_NORMAL (16) /* 32 */ |