This commit adds functions:
* secp256k1_rand_bits, which works like secp256k1_rand32, but consumes
less randomness
* secp256k1_rand_int, which produces a uniform integer over any range
* secp256k1_rand_bytes_test, which works like secp256k1_rand256_test
but for arbitrary byte array
This also makes use of optional valgrind instrumentation if -DVALGRIND
is set.
This also moves secp256k1.c above secp256k1.h in tests.c or otherwise
we get non-null macros on the public functions which may defeat some
of the VERIFY checks.
Libtool will do the right thing and use whatever is available
based on --enable-shared/--enable-static.
This also means that some of the things we build actually
test the dynamic library.
This makes it more clear that a null check is intended. Avoiding the
use of a pointer as a test condition alse increases the type-safety
of the comparisons.
(This is also MISRA C 2012 rules 14.4 and 11.9)
486b9bb Use a flags bitfield for compressed option to secp256k1_ec_pubkey_serialize and secp256k1_ec_privkey_export (Luke Dashjr)
05732c5 Callback data: Accept pointers to either const or non-const data (Luke Dashjr)
1973c73 Bugfix: Reinitialise buffer lengths that have been used as outputs (Luke Dashjr)
788038d Use size_t for lengths (at least in external API) (Luke Dashjr)
c9d7c2a secp256k1_context_set_{error,illegal}_callback: Restore default handler by passing NULL as function argument (Luke Dashjr)
9aac008 secp256k1_context_destroy: Allow NULL argument as a no-op (Luke Dashjr)
64b730b secp256k1_context_create: Use unsigned type for flags bitfield (Luke Dashjr)
This has the effect of making `secp256k1_scalar_mul_shift_var` constant
time in both input scalars. Keep the _var name because it is NOT constant
time in the shift amount.
As used in `secp256k1_scalar_split_lambda_var`, the shift is always
the constant 272, so this function becomes constant time, and it
loses the `_var` suffix.
Designed with clear separation of the wNAF conversion, precomputation
and exponentiation (since the precomp at least we will probably want
to separate in the API for users who reuse points a lot.
Future work:
- actually separate precomp in the API
- do multiexp rather than single exponentiation
- Add zero/one sanity check tests for ecmult
- Add unit test for secp256k1_scalar_split_lambda_var
- Typo fix in `ge_equals_ge`; was comparing b->y to itself, should
have been comparing a->y to b->y
- Normalize y-coordinate in `random_group_element_test`; this is
needed to pass random group elements as the first argument to
`ge_equals_ge`, which I will do in a future commit.
