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precompute only as needed, or will want to access some other expensive
resource or etc.
Change how the secret for generating blinding is done in cases where a
PRNG isn't available. Use the operations public op to hide the secret,
for instance the seed for a DH blinding variable is 2^x mod p.
Make use of being able to mutate internal structures in the RW signer,
since that does have access to a PRNG, so use it to initialize the
blinder on first call to sign().
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There are multiple unsatisfactory elements to the current solution,
as compared to how blinding was previously done:
Firstly, blinding is only used in the baseline implementations; the code
using OpenSSL and GMP is not protected by blinding at all.
Secondly, at the point we need to set up blinding, there is no access
to a PRNG. Currently I am going with a quite nasty solution, of using
a private key parameter to seed a simple PRNG constructed as:
SHA-512(TS1 || private_key_param || public_key_param || TS2)
I really want to fix both of these elements but I'm not sure how to do
so easily.
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