This allows us to finely control when to use a single hash or a double hash in
various places. For example, Bitcoin signatures use double SHA256, but Decred
signatures use a single BLAKE256. However, both use double hashes for Base58.
The bip32 private key derivation used bn_addmod to handle
wrap around. This was never sufficient as bn_addmod uses only
bn_fast_mod, so an additional bn_mod is necessary. The bn_fast_mod
helped when bn_mod was not side-channel safe. Now that bn_mod uses
constant time code, we can get rid of the unnecessary bn_fast_mod
step and use bn_add instead of bn_addmod.
This adds an is_canonic parameter to all sign functions. This is a
callback that determines if a signature corresponds to some coin
specific rules. It is used, e. g., by ethereum (where the recovery
byte must be 0 or 1, and not 2 or 3) and or steem signatures (which
require both r and s to be between 2^248 and 2^255).
This also separates the initialization and the step function of the
random number generator, making it easy to restart the signature
process with the next random number.
The new name of the function is `hdnode_get_ethereum_address`
and it gets a hdnode as input as opposed to a public key. This
also avoids first computing the compressed public key and then
uncompressing it.
Test cases were adapted to work with new function. The test-vectors
are the same as for bip32 and independently checked with an adhoc
python implementation.
Remove fingerprint from hdnode structure (if you need it, call
hdnode_fingerprint on the parent hdnode).
Only compute public_key, when hdnode_fill_public_key is called.
* Split ecdsa_curve into curve_info and ecdsa_curve to support bip32 on
curves that don't have a ecdsa_curve.
* Don't fail in key derivation but retry with a new hash.
* Adapted test case accordingly
