diff options
Diffstat (limited to 'src/crypto/zinc/poly1305/poly1305-arm-glue.h')
| -rw-r--r-- | src/crypto/zinc/poly1305/poly1305-arm-glue.h | 11 |
1 files changed, 11 insertions, 0 deletions
diff --git a/src/crypto/zinc/poly1305/poly1305-arm-glue.h b/src/crypto/zinc/poly1305/poly1305-arm-glue.h index c694524..92aa226 100644 --- a/src/crypto/zinc/poly1305/poly1305-arm-glue.h +++ b/src/crypto/zinc/poly1305/poly1305-arm-glue.h @@ -50,6 +50,17 @@ struct poly1305_arch_internal { }; #endif +/* The NEON code uses base 2^26, while the scalar code uses base 2^64 on 64-bit + * and base 2^32 on 32-bit. If we hit the unfortunate situation of using NEON + * and then having to go back to scalar -- because the user is silly and has + * called the update function from two separate contexts -- then we need to + * convert back to the original base before proceeding. The below function is + * written for 64-bit integers, and so we have to swap words at the end on + * big-endian 32-bit. It is possible to reason that the initial reduction below + * is sufficient given the implementation invariants. However, for an avoidance + * of doubt and because this is not performance critical, we do the full + * reduction anyway. + */ static void convert_to_base2_64(void *ctx) { struct poly1305_arch_internal *state = ctx; |