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Updates to documentation for SHA256 build options. Changed to enable Ch/Maj math based of specification by default.

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The `WOLFSSL_SHA256_ALT_CH_MAJ` alternate Ch/Maj performance is the same.
The `SHA256_MANY_REGISTERS` is about 13% slower on 64-bit. On some platforms is slightly faster.
This commit is contained in:
David Garske
2019-06-03 14:17:47 -07:00
parent ebbfe769e3
commit b4571f1f5a
1 changed files with 25 additions and 2 deletions
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27
wolfcrypt/src/sha256.c
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@ -25,6 +25,24 @@
#include <wolfssl/wolfcrypt/settings.h> #include <wolfssl/wolfcrypt/settings.h>
/*
* SHA256 Build Options:
* USE_SLOW_SHA256: Reduces code size by not partially unrolling
(~2KB smaller and ~25% slower) (default OFF)
* WOLFSSL_SHA256_BY_SPEC: Uses the Ch/Maj based on SHA256 specification
(default ON)
* WOLFSSL_SHA256_ALT_CH_MAJ: Alternate Ch/Maj that is easier for compilers to
optimize and recognize as SHA256 (default OFF)
* SHA256_MANY_REGISTERS: A SHA256 version that keeps all data in registers
and partial unrolled (default OFF)
*/
/* Default SHA256 to use Ch/Maj based on specification */
#if !defined(WOLFSSL_SHA256_BY_SPEC) && !defined(WOLFSSL_SHA256_ALT_CH_MAJ)
#define WOLFSSL_SHA256_BY_SPEC
#endif
#if !defined(NO_SHA256) && !defined(WOLFSSL_ARMASM) #if !defined(NO_SHA256) && !defined(WOLFSSL_ARMASM)
#if defined(HAVE_FIPS) && \ #if defined(HAVE_FIPS) && \
@ -582,10 +600,14 @@ static int InitSha256(wc_Sha256* sha256)
0x90BEFFFAL, 0xA4506CEBL, 0xBEF9A3F7L, 0xC67178F2L 0x90BEFFFAL, 0xA4506CEBL, 0xBEF9A3F7L, 0xC67178F2L
}; };
/* Both versions of Ch and Maj are logically the same, but with the second set
the compilers can recognize them better for optimization */
#ifdef WOLFSSL_SHA256_BY_SPEC #ifdef WOLFSSL_SHA256_BY_SPEC
/* SHA256 math based on specification */
#define Ch(x,y,z) ((z) ^ ((x) & ((y) ^ (z)))) #define Ch(x,y,z) ((z) ^ ((x) & ((y) ^ (z))))
#define Maj(x,y,z) ((((x) | (y)) & (z)) | ((x) & (y))) #define Maj(x,y,z) ((((x) | (y)) & (z)) | ((x) & (y)))
#else #else
/* SHA256 math reworked for easier compiler optimization */
#define Ch(x,y,z) ((((y) ^ (z)) & (x)) ^ (z)) #define Ch(x,y,z) ((((y) ^ (z)) & (x)) ^ (z))
#define Maj(x,y,z) ((((x) ^ (y)) & ((y) ^ (z))) ^ (y)) #define Maj(x,y,z) ((((x) ^ (y)) & ((y) ^ (z))) ^ (y))
#endif #endif
@ -679,6 +701,7 @@ static int InitSha256(wc_Sha256* sha256)
return 0; return 0;
} }
#else #else
/* SHA256 version that keeps all data in registers */
#define SCHED1(j) (W[j] = sha256->buffer[j]) #define SCHED1(j) (W[j] = sha256->buffer[j])
#define SCHED(j) ( \ #define SCHED(j) ( \
W[ j & 15] += \ W[ j & 15] += \
@ -707,7 +730,7 @@ static int InitSha256(wc_Sha256* sha256)
{ {
word32 S[8], t0, t1; word32 S[8], t0, t1;
int i; int i;
word32 W[16]; word32 W[WC_SHA256_BLOCK_SIZE/sizeof(word32)];
/* Copy digest to working vars */ /* Copy digest to working vars */
S[0] = sha256->digest[0]; S[0] = sha256->digest[0];
@ -744,7 +767,7 @@ static int InitSha256(wc_Sha256* sha256)
return 0; return 0;
} }
#endif #endif /* SHA256_MANY_REGISTERS */
#endif #endif
/* End wc_ software implementation */ /* End wc_ software implementation */